Modified hyaluronic acid polymer compositions and related methods

ABSTRACT

The present application provides compositions comprising hyaluronic acid having low levels of functional group modification, mixtures formed by controlled reaction of such lightly modified hyaluronic acid with suitable difunctional or multi-functional crosslinkers, and hydrogel precursor compositions and the resulting hydrogels. The compositions are lightly cross-linked and possess low pro-inflammatory properties when injected in vivo, and can be used as, for example, medical devices, biomedical adhesives and sealants, and for localized delivery of bioactive agents, among other uses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/929,115, filed Oct. 30, 2015, now U.S. Pat. No. 9,446,136, which is acontinuation of U.S. application Ser. No. 14/333,426, filed Jul. 16,2014, now U.S. Pat. No. 9,192,678, which is a continuation of U.S.application Ser. No. 13/387,682 filed Jan. 27, 2012, now U.S. Pat. No.8,790,702, which is a U.S. National Stage of International PatentApplication No. PCT/US2010/043108, filed Jul. 23, 2010, which claims thebenefit of priority to U.S. Provisional Application No. 61/311,953,filed Mar. 9, 2010 and to U.S. Provisional Application No. 61/230,074,filed Jul. 30, 2009, the contents each of which is incorporated hereinby reference in its entirety.

FIELD

The disclosure relates generally to hyaluronic acid having low levels offunctional group modification, mixtures formed by controlled reaction ofsuch lightly modified hyaluronic acid with suitable difunctional ormulti-functional reactants, and related hydrogel and hydrogel precursorcompositions. The compositions described herein are lightly cross-linkedand possess low pro-inflammatory properties when injected in vivo, andcan be used as, for example, medical devices, biomedical adhesives andsealants, and for localized delivery of bioactive agents, among otheruses.

BACKGROUND

Hyaluronic acid is a naturally-occurring, anionic, non-sulfatedglycosaminoglycan that is distributed widely throughout connective,epithelial, and neural tissues. The average 70 kg (154 lbs.) personpossesses roughly 15 grams of hyaluronic acid in his/her body, one-thirdof which is turned over (degraded and synthesized) every day (Stern R.Eur J Cell Biol 83 (7): 317-25, (2004)). Since hyaluronic acid is foundnaturally in many tissues of the body and is therefore biocompatible, itis believed to be well suited to biomedical applications. Indeed, manypolymeric materials, including hyaluronic acid (also referred to ashyaluronan), derivatized forms thereof, and its conjugates, can be usedas injectable biomaterials, as well as in medical devices andimplantable materials. Applications include delivery of therapeuticmolecules to a localized site, use as adhesives or sealants, in tissueengineering, as viscosupplements, and in wound healing. Hyaluronic acid,when administered and used as a therapeutic in its naturally occurringform, is typically rapidly cleared from the body, making frequentadministration necessary. Although often a polymeric gel or gelprecursor may demonstrate favorable properties in terms of reactionchemistry and conditions, gellation characteristics, and/or therapeuticeffect in one or more in-vitro models, in certain instances, sucheffects fail to translate into beneficial properties in vivo or in aclinical setting.

SUMMARY

In a first aspect, provided is a hyaluronic acid modified to a degree of10% or less by reaction with divinyl sulfone. Specifically, thehyaluronic acid possesses 10% or less of its hydroxyl groups derivatizedby an addition reaction with divinyl sulfone.

In a particular embodiment, the hyaluronic acid has 1-10% of itshydroxyl groups derivatized to 2-(vinylsulfonyl)ethoxy groups. Theresulting activated hyaluronic acid, having a low level of divinylsulfone activation is referred to generally herein as(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid or “VS-HA”.

In yet another embodiment, the hyaluronic acid has a degree ofconversion of hydroxyl groups to 2-(vinylsulfonyl)ethoxy groups selectedfrom 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%.

In yet a more specific embodiment, the hyaluronic acid has a degree ofconversion of hydroxyl groups to 2-(vinylsulfonyl)ethoxy groups of about4-5% per disaccharide repeat unit.

In yet another embodiment, the(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid possesses a molecularweight ranging from about 700 to about 3 million Daltons.

In a second aspect, provided is a hydrogel formed by reaction of(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid with a thiolcrosslinker having two or more thiol groups.

In a related embodiment, the thiol crosslinker possesses from two toabout 8 thiol groups. In yet another embodiment, the thiol crosslinkerpossesses a number of thiol groups selected from 2, 3, 4, 5, 6, 7, and8.

In yet another embodiment directed to the second aspect, the thiolcrosslinker is a thiol-functionalized polyethylene glycol (PEG) (i.e., aPEG-thiol).

In an additional embodiment of the foregoing, the polyethylene glycolthiol possesses a molecular weight ranging from about 250 about 20,000daltons.

In a related embodiment, the thiol-functionalized polyethylene glycol islinear and possesses a thiol group at each terminus, i.e., ispolyethylene glycol dithiol (PEG dithiol).

In yet another embodiment, the thiol-functionalized polyethylene glycolis four-armed and possesses a pentaerythritol core.

In yet another embodiment, the thiol-functionalized polyethylene glycolpossesses a polyol core selected from glycerol, glycerol dimer(3,3′-oxydipropane-1,2-diol) trimethylolpropane, sorbitol,pentaerythritol, and hexaglycerol.

In a further embodiment, the hydrogel formed by reaction of(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid with a thiolcrosslinker contains less than ten percent of unreacted thiol and lessthan 10% of unreacted vinyl sulfone groups. The quantity of residual,unreacted thiol groups can be determined, for example, using theEllman's test.

In yet an additional embodiment, a hydrogel formed by reaction of(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid with a thiolcrosslinker contains a percent by weight (wt/wt) of polymer to waterranging from about 0.5 to 5.0 percent. Illustrative percents by weightof polymer to water for the resulting hydrogel are, in one or moreembodiments, selected from 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5and 5 percent.

In yet another embodiment, the hydrogel formed by reaction of(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid with a thiolcrosslinker is in the form of particles having a size ranging from about0.10 to 3.0 millimeters.

In yet another embodiment, the foregoing hydrogel particles are in theform of an aqueous slurry.

In yet a further embodiment, the hydrogel as described in any one ormore of the foregoing embodiments is dispersed in an aqueous solution ofunmodified hyaluronic acid.

In yet an additional and more specific embodiment, provided is acomposition comprising crosslinked hydrogel particles in a solution ofhyaluronic acid in saline, where the hydrogel particles are formed byreaction of polyethylene glycol dithiol (PEG-dithiol) with hyaluronicacid having 1-10% of its hydroxyl groups derivatized with2-(vinylsulfonyl)ethoxy groups.

In yet an additional embodiment, the hydrogel as described in any one ormore of the foregoing embodiments comprises a bioactive agent. In aspecific embodiment, the bioactive agent is a corticosteroid. In yet amore particular embodiment, the bioactive agent is triamcinoloneacetonide.

In yet an alternative embodiment, the hydrogel as described in any oneor more of the foregoing embodiments comprises living cells.

In a further embodiment, the hydrogel formed by reaction of(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid with a bifunctional orgreater thiol crosslinker exhibits low pro-inflammatory properties in agoat joint injection model.

In a particular embodiment, the hydrogel exhibits low pro-inflammatoryproperties as indicated by leukocyte response in associated synovialfluid.

In yet another particular embodiment, the hydrogel exhibits lowpro-inflammatory properties in a goat joint injection model as indicatedby gross observational scoring.

In yet an additional embodiment, the hydrogel is sterile.

In yet a further embodiment, a hydrogel as provided herein is packagedin a syringe.

In yet a further embodiment, provided is a method of administering anyof the herein described hydrogel compositions into an intra-articularspace of a joint of a subject.

In yet a third aspect, provided is a method of preparing(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid. The method comprisesreacting hyaluronic acid with divinyl sulfone under reaction conditionseffective to react no more than about 10% of hydroxyl groups on thehyaluronic acid disaccharide repeat units with the divinyl sulfone toform (2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid.

In a related embodiment, the reacting comprises reacting hyaluronic acidwith a molar excess of divinyl sulfone.

In a further embodiment, the reacting step is carried out under ambientconditions.

In yet another embodiment, the reacting step is carried out for 10seconds to about 120 seconds under ambient conditions.

In yet another embodiment, the reacting step is carried out in aqueousbase.

In a further embodiment, the method further comprises quenching thereaction by addition of acid. In a related embodiment, sufficient acidis added to adjust the pH to a range from about 4 to 6.5.

In a fourth aspect, described herein is a method of preparing ahydrogel. The method comprises reacting(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid with a thiolcrosslinker having two or more thiol groups under reaction conditionseffective to form a crosslinked hydrogel. Suitable thiol crosslinkingagents include thiol-functionalized polyethylene glycol, alkane-dithiolsand the like.

In a related embodiment, the reacting is carried out at physiologicalpH.

In yet another embodiment, the reacting is carried out in the absence ofa polymerization initiator.

In yet another embodiment, the reacting is carried out in the absence ofapplication of an external energy source.

In yet another embodiment, the reacting is carried out at a temperatureranging from 20° C. to 45° C.

In yet a further embodiment, the hydrogel comprises 10% or less ofunreacted vinyl sulfone or thiol groups. Preferably, the hydrogelcomprises 5% or less of unreacted sulfone or thiol groups. In a specificembodiment, the hydrogel comprises essentially no detectable unreactedvinyl sulfone or thiol groups.

In a fifth aspect, provided is a kit comprising syringe, where thesyringe comprises a hydrogel formed by reaction of(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid with a thiolcrosslinker as described above.

In yet another related embodiment, the syringe comprises a hydrogel asdescribed in any one or more of the above embodiments where the hydrogelis dispersed in an aqueous solution of unmodified hyaluronic acid. In arelated embodiment, the aqueous solution is saline.

In a related embodiment, the syringe is in a form suitable forintra-articular injection of the hydrogel using a 18-21 gauge needle.

In yet another related embodiment, the syringe comprises a hydrogel asdescribed in any one or more of the above embodiments where the hydrogelfurther comprises a bioactive agent. In a related embodiment, thebioactive agent is selected from the group consisting of steroids,growth factors, anti-proliferative agents, and antibiotics. In yet amore specific embodiment, the hydrogel comprises from about 0.01% toabout 20% by weight bioactive agent, depending of course on the potencyof the bioactive agent. That is to say, a less potent agent willtypically be contained in the hydrogel at the higher end of theforegoing range, e.g., from about 10-20% by weight, while a potentbioactive agent will be at the lower end of the range, e.g., from about0.01 to 3% by weight. In a specific embodiment in which the bioactiveagent is triamcinolone acetonide, the hydrogel comprises from about 0.1to 1% by weight bioactive agent.

In yet another embodiment, the syringe comprises a hydrogel as describedin any one or more of the above embodiments where the hydrogel furthercomprises living cells. Exemplary living cells include stem cells,parenchimal stem cells, blood-derived cells, and bone marrow cells.

In a sixth aspect, provided is a method for delivering a poorly watersoluble bioactive agent by administering a hydrogel as described hereincomprising the poorly water soluble bioactive agent dispersed in thehydrogel.

In a seventh aspect, described is a method of treating acute and chronicinflammation associated with osteoarthritis, rheumatoid arthritis, otherinflammatory arthritides, and repetitive use by injecting a hydrogel inaccordance with any one or more aspects or embodiments described hereininto the intra-articular space of a joint such as the knee in a subject.In a particular embodiment, i.e., when the hydrogel comprises acorticosteroid incorporated therein, the method is effective to resultin damage to the cartilage that is reduced from the cartilage damagethat occurs upon administration of an equivalent amount of thecorticosteroid absent hydrogel entrapment, as characterized in a goatjoint injection model by total Mankin score at 28 days post injection.In a related embodiment, the foregoing method, i.e., injection of thehydrogel into the intra-articular space of a joint, is effective toprovide to the subject a degree of pain relief relative to the painexperienced by the subject prior to injection of the subject hydrogel.Typically, initiation of pain relief is experienced by the subjectwithin anywhere from about one hour to about one week following theinjection, more preferably within about one hour to about 3 daysfollowing injection. That is to say, initiation of pain relief typicallycommences within about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 hours post injection, or, ifnot within the first twenty four hours, within 1, 2, 3, 4, 5, 6, or 7days post-injection. Typically, the duration of pain relief is expectedto last anywhere from about 3 to 9 months, i.e., from 3, 4, 5, 6, 7, 8,9 months or even longer.

In an eighth aspect, provided is a method for reducing damage tocartilage upon administration of a corticosteroid into theintra-articular space of a joint of a subject suffering fromosteoarthritis by incorporating the corticosteroid into a cross-linkedhydrogel prior to or upon administration to the subject. Thecross-linked hydrogel is generally a hyaluronic acid-based hydrogel tobe described in greater detail below. An exemplary cross-linked hydrogelis one that is a hyaluronic acid modified to a degree of 10% or less byreaction with divinyl sulfone, followed by cross-linking with a thiolcrosslinker having two or more thiol groups. Surprisingly, by virtue ofincorporating the corticosteroid into the cross-linked hydrogel, lessdamage occurs to the cartilage than occurs upon administration of anequivalent dose of corticosteroid absent hydrogel incorporation.

In a ninth aspect related to the foregoing, in a method for treatingosteoarthritis by administering a therapeutically effective amount of acorticosteroid into the intra-articular space of a joint of a subject,provided herein is an improvement comprising administering thecorticosteroid in the form of a cross-linked hydrogel compositioncomprising the corticosteroid, whereby damage to the cartilage islessened when compared to administration of an equivalent amount of thecorticosteroid absent hydrogel incorporation.

In a particular embodiment related to the seventh, eighth and ninthaspects, the corticosteroid is selected from the group consisting ofhydrocortisone, hydrocortisone acetate, cortisone acetate, tixocortolpivalate, prednisolone, methylprednisolone, prednisone, triamcinolone,triamcinolone salts such as triamcinolone acetonide, triamcinolonebenetonide, triamcinolone furetonide, triamcinolone hexacetonide,triamcinolone diacetate, triamcinolone alcohol, mometasone, amcinonide,budesonide, desonide, fluocinonide, fluocinolone acetonide, halcinonide,betamethasone, betamethasone sodium phosphate, dexamethasone,dexamethasone sodium phosphate, fluocortolone,hydrocortisone-17-butyrate, hydrocortisone-17-valerate, aclometasonedipropionate, betamethasone valerate, betamethasone dipropionate,prednicarbate, clobetasone-17-butyrate, clobetasol-17-propionate,fluocortolone caproate, fluocortolone pivalate, fluprednidene acetate,beclomethasone dipropionate monohydrate, flunisolide, fluticasonepropionate, mometasone furoate monohydrate, and fluticasone furoate.

In an even more specific embodiment, the corticosteroid is triamcinoloneacetonide.

In a tenth aspect, provided is a formulation comprising a poorlywater-soluble soluble drug such as a steroid entrapped within the3-dimensional structure of a hydrogel as described herein, followed byinjecting such formulation into the intra-articular space of a joint.

In one embodiment related to the foregoing, the trapping of steroidparticles within the hydrogel is effective to prevent direct contact ofthe majority of the steroid particles with the joint tissues.

In yet another related embodiment, the trapping of steroid particles inthe hydrogel is effective to maximize the localized concentration of thesteroid in the joint, while minimizing its systemic concentration.

In yet a further embodiment, the entrapment of steroid particles in thehydrogel is effective to protect the steroid particles from prematureclearance from the joint.

In yet an additional embodiment, by entrapping the steroid in thehydrogel, therapeutic efficacy of the steroid is attained at a lowertotal dose than would be attained absent hydrogel entrapment, whileminimizing unwanted local and systemic side effects.

In a related aspect, provided is the use of a hydrogel as describedherein for injecting or implanting onto or into bone, teeth, nerves,cartilage, blood vessels, soft tissues or other tissues of a mammaliansubject.

Additional embodiments of the compositions, methods, kits, and the likewill be apparent from the following description, examples, and claims.As can be appreciated from the foregoing and following description, eachand every feature described herein, and each and every combination oftwo or more of such features, is included within the scope of thepresent disclosure provided that the features included in such acombination are not mutually inconsistent. In addition, any feature orcombination of features may be specifically excluded from any embodimentof the present invention. Additional aspects and advantages of thepresent invention are set forth in the following description,particularly when considered in conjunction with the accompanyingexamples and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ¹H NMR spectrum of vinyl-sulfone modified hyaluronic acid(HA-VS) prepared as described in Example 1. Based upon the NMR, thehyaluronic acid was determined to possess a level of vinyl sulfonesubstitution of approximately four percent per disaccharide.

FIG. 2 is a plot demonstrating percent release of a poorly water solublemodel drug, triamcinolone acetonide, versus sampling number as describedin Example 16.

FIG. 3 is a plot demonstrating the cumulative mass released of a poorlywater soluble model drug, triamcinolone acetonide, per sampling point asdescribed in Example 16.

FIG. 4 is a plot demonstrating the amount of triamcinolone acetonidereleased per sampling point as described in Example 16.

FIG. 5 is a graphical depiction of the synovial fluid leukocyte count(cells per cubic millimeter) in goat knees injected with Test Material 1relative to the test material treatment group evaluated at 24 hrs after1.5 ml injection as described in Example 17. Test Material1=HA-VS/PEG-(SH)₂ gel.

FIG. 6 is a graphical depiction of the absolute synovial fluid leukocytecount (absolute=total volume×synovial fluid leukocyte count) in goatknees injected with Test Material 1 relative to test material treatmentgroup evaluated at 24 hrs after 1.5 ml injection as described in Example17. Test Material 1=HA-VS/PEG-(SH)₂ gel.

FIG. 7 provides a graphical representation of the synovial fluidleukocyte differential distribution (means for groups) for the injectedgoat knees relative to test material treatment group evaluated at 24hrs. after 1.5 ml injection as described in Example 17. Shown for eachTest Material is the distribution of polymorphonuclear leukocytes (PMN),lymphocytes, monocytes, and eosinophils (Eos).

FIG. 8 is a graphical depiction of the average total scores for synovialfluid, joint tissues, and combined synovial fluid and joint tissuesscores (Table 6) for the injected goat knees for each representativeTest Material as described in Example 17, where Total GrossScore=Synovial Fluid Score+Total Joint Score. Maximum score for SynovialFluid or Total Joint Score is 8 with 0 being normal; Maximum score forTotal Gross Score is 16 with 0 being normal.

FIG. 9 illustrates the safranin O stain scores for cartilage samplesfrom goat joints treated with the test materials as described in detailin Example 34 at 14 days post injection. Test Material 1:HA-VS-PEG-(SH)_(2;) Test Material 2: HA-VS-PEG-(SH)₂-TA.

FIG. 10 illustrates the safranin O stain scores for cartilage samplesfrom goat joints treated with the test materials as described in detailin Example 34 at 28 days post injection.

FIG. 11 illustrates the results of the Mankin scoring systems forcartilage samples from goat joints treated with the test materials asdescribed in detail in Example 34 at 28 days post-treatment.

FIG. 12 and FIG. 13 illustrate representative medial femoral condylehistology with Safranin-O staining (40×) at Day 14 (FIG. 12) and Day 28(FIG. 13) post-injection, respectively, as described in detail inExample 34.

FIG. 14 provides a graphical representation of mean synovial fluidleukocyte count (mean+sd) for all animals relative to the Test Materialand Control Material evaluated 24 hours after 1.5 ml intra-articularinjection as described in detail in Example 45.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter. Thisinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein; rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the invention to thoseskilled in the art.

All publications, patents and patent applications cited herein, whethersupra or infra, are hereby incorporated by reference in their entirety,unless otherwise indicated. In an instance in which the same term isdefined both in a publication, patent, or patent applicationincorporated herein by reference and in the present disclosure, thedefinition in the present disclosure represents the controllingdefinition. For publications, patents, and patent applicationsreferenced for their description of a particular type of compound,chemistry, etc., portions pertaining to such compounds, chemistry, etc.are those portions of the document which are incorporated herein byreference.

Definitions

It must be noted that, as used in this specification, the singular forms“a,” “an,” and “the” include plural referents unless the context clearlydictates otherwise. Thus, for example, reference to a “polymer” includesa single polymer as well as two or more of the same or differentpolymers.

Unless specifically noted otherwise, definitions of the terms herein arestandard definitions used in the arts of organic synthesis, and polymerand pharmaceutical science.

In describing and claiming the present invention, the followingterminology will be used in accordance with the definitions describedbelow.

A “biocompatible polymer” is a polymer having degradation products thatare compatible with living tissue, or that may have beneficialbiological properties. The biocompatible polymer may be biocompatible initself, and/or may be synergistically biocompatible when employed inconjunction with a biologically active agent.

The term “hyaluronic acid polymer” refers to a polymer comprising repeatdisaccharide subunits of hyaluronan, where the repeat units may bederivatized at one or more positions of the D-glucuronic acid and/or theD-N-acetylglucosamine unit of the disaccharide repeat subunit. Ahyaluronic acid polymer is meant to encompass hyaluronic acid (alsoreferred to as hyaluronan), derivatized hyaluronic acid, salts forms,hyaluronic acid linker complexes, and hyaluronic acid conjugates. Theterm, “hyaluronic acid”, is meant to refer to unmodified ornon-derivatized hyaluronic acid.

The terms “hyaluronic acid derivative” or “derivatized hyaluronic acid”or “modified hyaluronic acid” refers to hyaluronic acid that has beenderivatized by reaction with, e.g., one or more small chemical moietiessuch as divinyl sulfone or the like.

A thiol-derivatized hyaluronic acid polymer refers to a hyaluronic acidpolymer as described above having three or more disaccharide repeatunits and comprising at least one sulfhydryl (thiol) group.

The term “reactive” refers to a functional group (e.g., present in apolymer) that reacts readily or at a practical rate under conventionalconditions of organic synthesis. This is in contrast to those groupsthat either do not react or require strong catalysts or impracticalreaction conditions in order to react (i.e., a “nonreactive” or “inert”group).

“Molecular mass” or molecular weight, as used herein, in the context ofa water-soluble polymer such as hyaluronic acid, refers to the nominalaverage molecular mass of a polymer determined by multi angle lightscattering. Molecular weight can be expressed as either a number-averagemolecular weight or a weight-average molecular weight. Unless otherwiseindicated, all references to molecular weight herein refer to thenumber-average molecular weight.

The term “hydrogel” refers to a water-containing three dimensionalhydrophilic polymer network or gel in which the water is the continuousphase and in which the water content is greater than 50% (w/w). Thehydrogels described herein typically do not require the incorporation ofcross-linking initiators or accelerants to achieve the desired degree ofcrosslinking.

A “sterile” composition is one that is free of viable microbes asdetermined using the USP sterility test. See “The United StatesPharmacopeia”, 30th Revision, The United States PharmacopeialConvention: 2008.

The term “lightly crosslinked” as used herein or “having a low degree ofcrosslinking” means that the crosslinking reaction occurs such thatabout 40% to about 100% of the available crosslinking sites are reactedto generate the final crosslinked gels, where the modified hyaluronicacid starting material used to form the gel possesses 10% or less of itshydroxyl groups in activated/derivatized form, to thereby provide anhydrogel that is considered overall to be lightly crosslinked.

A hydrogel that exhibits low pro-inflammatory properties in a goat jointinjection model is one that when evaluated in a goat joint injectionmodel as described herein exhibits a synovial fluid leukocyte count ofless than 20,000 cells per cubic millimeter at 24 hours post-injection,and preferably, a synovial fluid leukocyte count of less than 15,000cells per cubic millimeter at 24 hours post-injection, where the countis an average count taken from three individual injected animals.

A hydrogel containing a corticosteroid that “reduces damage to thecartilage” or “that produces less cartilage damage” than an equivalentdose of a corticosteroid administered absent incorporation into thesubject hydrogel is typically characterized by any suitable model forassessing cartilage damage, but preferably, is measured using an in-vivogoat knee injection model as described in detail herein. Post injectiondata is typically collected at least 7 days but no more than 28 dayspost injection. A preferred standard of measure is total Mankin score; amaterial that reduces damage to cartilage over drug alone, assessed asdescribed previously, is one that demonstrates an improvement in theaverage score over the drug (i.e., corticosteroid), when administered inan equivalent amount. Preferably, the total Mankin score forhydrogel-incorporated drug is improved by at least one or more pointsover the total Mankin score for drug when administered in non-hydrogelentrapped form.

The term “drug,” or “pharmaceutically active agent” or “bioactiveagent,” or “active agent” as used interchangeably, means any organic orinorganic compound or substance having bioactivity and adapted or usedfor therapeutic purposes. Proteins, hormones, anti-cancer agents, smallmolecule chemical compounds and mimetics, oligonucleotides, DNA, RNA andgene therapies are included under the broader definition of “drug”. Asused herein, reference to a drug, as well as reference to other chemicalcompounds herein, is meant to include the compound in any of itspharmaceutically acceptable forms, including isomers such asdiastereomers and enantiomers, salts, solvates, and polymorphs,particular crystalline forms, as well as racemic mixtures and pureisomers of the compounds described herein, where applicable.

The term “solid” as used herein, means a non-fluid substance, includingcrystalline forms, their polymorphs, non-crystalline amorphoussubstances, precipitates, and particles, or the like. Each of thesesolid forms may vary in size, from about 0.01 microns to 2,000 microns,for example, from about 0.01 microns to 1 micron, from 1 micron to 100microns, from 100 microns to 1,000 microns, from 1000 microns to 2000microns, from 1100 microns to 1500 microns, and from 1500 microns to2000 microns.

Particle sizes, as referred to herein, refer to particle diameters, andare typically determined by sieve analysis. The sizes or rangesdescribed typically correspond to a sieve or mesh opening size. One mayrefer to a particle size conversion chart to determine the size, e.g.,in mm, corresponding to a particular mesh or screen number. See, e.g.,Examples 39 and 40.

A “water insoluble drug” or “poorly water soluble drug” is one having anaqueous solubility below 10 mg/mL.

The terms “effective amount” or “pharmaceutically effective amount” or“therapeutically effective amount” of a composition (or hydrogel orpolymer), as provided herein, refer to a non-toxic but sufficient amountof the composition to provide the desired response, such as preventing,diminishing, or eliminating pain in a subject. The exact amount requiredwill vary from subject to subject, depending on the species, age, andgeneral condition of the subject, the severity of the condition beingtreated, the particular drug or drugs employed, specifics of thecomposition, mode of administration, and the like. An appropriate“effective” amount in any individual case may be determined by one ofordinary skill in the art using routine experimentation.

“Treatment” or “treating” acute or subchronic pain includes: inhibitingpain, i.e., arresting the development or reversing pain, or relievingpain, i.e., decreasing the amount of pain experienced by the subject.

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.

The term “substantially” in reference to a certain feature or entitymeans to a significant degree or nearly completely (i.e. to a degree of85% or greater) in reference to the feature or entity.

The term “about”, particularly in reference to a given quantity, ismeant to encompass deviations of plus or minus five percent.

Additional definitions may also be found in the sections which follow.

Overview

The present application is based, at least in part, on the inventors'discovery of hydrogels having extremely low pro-inflammatory propertieswhen administered in vivo. In conducting studies related to the presentdisclosure, the inventors recognized that many biocompatible hydrogelshaving seemingly beneficial chemical, rheological, and other physicalproperties, and which behave favorably in a number of biocompatible andaccepted in-vitro and in-vivo models, can cause inflammation and pain,in particular upon intra-articular injection. The materials describedherein were discovered to possess remarkably low pro-inflammatoryproperties when examined in a goat joint injection model and compared tosimilar hydrogel compositions. See, e.g., Example 17 and FIGS. 4-8.Generally, the instant hydrogels, when administered into anintra-articular space of a joint (e.g., when examined in a goat jointinjection model), exhibited reduced adverse or undesirable side effectson the cartilage when compared to the administration into anintra-articular space of a joint of an equivalent amount of either acommercially available viscosupplement or the administration of anequivalent amount of active agent absent hydrogel incorporation asdescribed herein.

Unexpectedly, it has also been discovered that the incorporation of acorticosteroid into a cross-linked hydrogel such as described hereinactually results in less damage to cartilage than observed uponadministration of an equivalent or higher dose of corticosteroid innon-hydrogel entrapped form. See, e.g., Example 34 and FIGS. 9-13.Moreover, provided herein are results indicating that intra-articularinjection of the instant hydrogels produces no local or systemiceffects—either when administered alone (i.e., absent active agent) orwhen administered in combination with a corticosteroid such astriamcinolone acetonide.

The superior hydrogels described herein are generally formed bycontrolled reaction of hyaluronic acid having well-characterized, lowlevels of functional group modification with suitable difunctional ormulti-functional crosslinkers. The resulting hydrogels are formed undermild conditions—without the need for initiators or accelerants or otherdeleterious additives. The resulting hydrogels are designed to possess aminimal number of unreacted, reactive groups, and are formed from aminimal number of reactants and reaction components. The hydrogels arelightly cross-linked, and have also been shown to be useful forentrapping and releasing bioactive agents in a sustained and steadyfashion over time. See, e.g., FIGS. 2-3.

The features of the composition, method and kits, and the like will nowbe discussed in greater detail below.

Derivatized Hyaluronic Acid Polymers

The present hydrogels can be formed from a variety of polymer materials.Preferred are biodegradable or bioabsorbable polymers modified to acertain extent to contain one or more reactive functionalities.Preferably, the polymer is a polyanionic polysaccharide (PAS).Non-exclusive examples of polyanionic polysaccharides include, forexample, hyaluronic acid (HA), carboxymethylcellulose (CMC),carboxymethylamylose (CMA), chondroitin-4-sulfate,chondroitin-6-sulfate, dermatan sulfate, dermatin-6-sulfate, heparinsulfate, heparin, keratin sulfate and their derivatives, andcombinations thereof. Such polymers are known in the art, and described,for example, in U.S. Pat. No. 6,056,970. Other biodegradable polymersinclude fibrin, fibrinogen, starch, poly(amino acids); peptides,proteins, gelatin and collagen.

A preferred polymer is hyaluronic acid also referred to as hyaluronan.Hyaluronic acid is a naturally occurring linear polysaccharide composedof alternating disaccharide units of N-acetyl-D-glucosamine andD-glucuronic acid joined by alternating β 1→3 glucuronidic and β 1→4glucosaminidic bonds, so that the repeating unit is(1→4)-β-D-GlcA-(1→3)-β-D-GlcNAc. The hyaluronic acid for use inpreparing one or more of the subject hydrogels is typically derivatizedwith one or more reactive moieties such as vinyl sulfone, acrylate,methacrylate, and the like. Preferably, the hyaluronic acid isderivatized with a single reactive moiety. The extent of modification orderivatization can range anywhere from 1% to 100% modification ofreactive functional groups within the polymer, although low levels ofpolymer modification are generally preferred.

One exemplary modified hyaluronic acid is hyaluronic acid derivatized byreaction of its hydroxyl groups with divinyl sulfone. The hyaluronicacid will typically have a degree of modification of reactive hydroxylgroups ranging from about 1 to about 80%. That is to say, a 1% degree ofmodification or substitution means that an average of 1% of thehyaluronic acid disaccharide units contain a vinyl sulrone group.Preferably, the hyaluronic acid will possess a degree of modification ofreactive hydroxyl groups ranging from about 1-50%. More, preferably, thehyaluronic acid will possess a degree of modification of reactivehydroxyl groups ranging from about 1 to about 25%. In a particularembodiment, the hyaluronic acid is modified to a degree of 10% or lessby reaction with divinyl sulfone. Specifically, in a preferredembodiment, the hyaluronic acid possesses 10% or less of its hydroxylgroups derivatized by an addition reaction with divinyl sulfone. Thehyaluronic acid hydroxyl groups are transformed to(2-(vinylsulfonyl)ethoxy) groups. The resulting activated hyaluronicacid is referred to generally herein as(2-(vinylsulfonyl)ethoxy)hyaluronic acid or VS-HA. In particular, thehyaluronic acid may possess a degree of conversion of hydroxyl groups to(2-(vinylsulfonyl)ethoxy) groups selected from the following: 1%, 2%,3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%. Alternatively, the hyaluronic acidmay possess a degree of conversion of hydroxyl groups falling within arange between any two of the foregoing percentages: e.g., from 1-10%,2-10%, 3-10%, 4-10%, and so forth for each and every combination ofintegers provided, e.g., from 2-7%, from 2-6%, from 3-8%, from 3-7%, andso forth. In yet a more specific embodiment, the hyaluronic acid has adegree of conversion of hydroxyl groups to (2-(vinylsulfonyl)ethoxy)groups of about 4-5% per disaccharide repeat unit. In certain instances,the level of hyaluronic acid functional group modification iswell-characterized (i.e., determined) to allow adjustment andoptimization of crosslinker concentration, along with other parameters,to thereby control the subsequent crosslinking reaction. The degree ofsubstitution/modification of the parent polymer can be determined by anyof a number of suitable methods, e.g., NMR, UV, or IR analysis, orelemental analysis. A preferred method for calculating percentsubstitution of a polymer such as hyaluronic acid is NMR, e.g., protonNMR. See, e.g., Example 1 in which degree of hyaluronic acidmodification was determined based upon the ratio of relative peak areascorresponding to the vinyl sulfone and the acetamide methyl group of thehyaluronic acid in the ¹H NMR spectrum.

The polymer may also comprise hydrazide-reactive groups and/oraminooxy-reactive groups as described in PCT/US/2004/040726 (WO2005/056608), relevant portions of the disclosure related toderivatization of such polymers and the resulting polymers themselvesbeing incorporated herein by reference in their entireties.

Alternatively, the polymer may be thiol-derivatized, such as athiol-derivatized hyaluronic acid. Exemplary thiol-derivatizedhyaluronic acid polymers include those described in U.S. Pat. Nos.6,884,788; 6,620,927; 6,548,081, 6,537,979; 6,013,679; U.S. Pat. No.5,502,081; and U.S. Pat. No. 5,356,883, relevant portions of whichrelated to such thiol-derivatized polymers being incorporated herein byreference in their entireties.

Additional examples of hyaluronic acid polymers includecysteine-derivatized hyaluronic acid, including but not limited to thosepolymers disclosed in “Controlled Release from Glycosaminoglycan DrugComplexes” R. V. Sparer et al., Chapter 6, pages 107-119, in T. J.Roseman et al., CONTROLLED RELEASE DELIVERY SYSTEMS, Marcel Dekker,Inc., New York (1983).

Examples of additional preferred polymers include hyaluronic acidderivatized by a pendent thiol group linked to an N-acyl urea group viaa hydrocarbyl, aryl, substituted-hydrocarbyl, or substituted aryl group.Illustrative polymers for use in the compositions and methods providedherein include Carbylan™-S (described in detail in International PatentPublication No. WO 2005/056608).

Additional derivatized polymers include hyaluronic acid covalentlyattached to a reactive linker such as a difunctional or multi-functionalacrylate, allyl or methacrylate compound. Representative linkers formodification of hyaluronic acid include, but are not limited to, poly(ethylene glycol)-diacrylate (PEGDA), poly (ethyleneglycol)-dimethacrylate (PEGDM), poly (ethylene glycol)-diacrylamide(PEGDAA) and poly (ethylene glycol)-dimethacrylamide (PEGDMA), andderivatives thereof. The PEG-moieties of the foregoing linkers may beoliogomeric or polymeric, for example, comprising from 2 to 100 or moresubunits. Additional linkers suitable for modification/functionalizationof a polymer such as hyaluronic acid include dextran acrylate, dextranmethacrylate, dextran glycidyl methacrylate, methacrylate functionalizedhyaluronic acid, acrylate functionalized hyaluronic acid, glyceroldimethacrylate, glycerol 1,3-diglycerolate diacrylate, sorbitol acrylateand derivatives thereof.

The derivatized hyaluronic acid or other polymer will typically possessan average molecular weight in the range of about 700 to 3,000,000daltons, Illustrative molecular weight ranges are from about 1,000 to2,000,000 daltons, or from about 5,000 to 1,000,000 daltons. Additionalsuitable molecular weight ranges include from about 50,000 daltons toabout 1,000,000 daltons, or from about 100,000 daltons to about1,200,000 daltons, or from about 90,000 daltons to about 300,000daltons. Molecular weights of hyaluronic acid are generally averagemolecular mass values, which can be determined, for example, bymulti-angle laser light scattering exclusion chromatography (MALLS-SEC).Depending upon its source, hyaluronic acid may have a polydispersity(M_(w)/M_(n)) of up to around 3, or more preferably, up to around 2.Generally, the hyaluronic acid starting material will have a rathernarrow molecular weight distribution, with values less than about 2.5,more preferably less than about 2. Exemplary polydispersities ofhyaluronic acid range from about 1.02 to about 2.5, where the startinghyaluronic acid may possess a polydispersity of about 1.02, 1.05, 1.1,1.2, 1.3, 1.3, 1.5, 1.6, 1.7, 1.8, 1.9, 2,0, 2.1, 2.2, 2.3, 2.4 or 2.5,or even greater. Alternatively, a suitable hyaluronic acid startingmaterial for derivatization may have a viscosity, typically incentipoise, at a specific concentration in water, that corresponds toany one or more of the average molecular weight ranges provided above.

Crosslinker

Examples of crosslinkers effective to form hydrogels having theadvantageous features described herein include compounds having two ormore reactive groups positioned upon a central molecule, “C”. Thecentral molecule may be a linear or cyclic alkane, a PEG oligomer orpolymer, or any other such suitable central molecule. In the case ofcrosslinkers that are PEG-based, the PEG may be linear, branched (havingtwo polymer arms), or multi-armed (e.g., having 3, 4, 5, 6, 7, 8 or morepolymer arms). Thus, in such instances, the central molecule willtypically a linear PEG, a branched PEG having 2 arms, or a multi-armedPEG having PEG arms emanating from a central core. Illustrative coresfor such multi-armed polymers include erythritol, pentaerythritol,trimethylolpropane, glycerol, glycerol dimer(3,3′-oxydipropane-1,2-diol), glycerol oligomers, sorbitol,hexaglycerol, and the like.

For example, the crosslinker may be a central molecule “C” having thiolor acrylate groups positioned thereon. A thiol-containing crosslinkercomprises two or more thiol groups. Such thiol groups will react with avinyl sulfone such as within a vinyl-sulfone derivatized hyaluronicacid. Illustrative thiol cross linkers include PEG-dithiol (HS-PEG-SH),3-arm PEG-tri-thiol (glycerine core), 4-arm PEG-tetrathiol(pentaerythritol core), or 8-arm PEG-octa-thiol (hexaglycerine core).The foregoing multi-armed PEG reagents may also have fewer than all armsfunctionalized with thiol. Additional suitable thiol reagents having PEGas the central molecule are available from Laysan Bio (Arab, Ala.), aswell as aromatic dithiols such as those available from NanoScience.Other suitable thiol crosslinkers include dimercaptosuccinic acid,2,3-dimercapto-1-propanesulfonic acid, dihydrolipoic acid, thiolfunctionalized dextran, and thiol-functionalized hyaluronic acid.Crosslinking agents having terminal acrylate groups positioned upon acentral molecule may also be used. For example, suitable for use ascrosslinking agents are central molecules as described above wherein thethiol groups are replaced with acylate or methacrylate groups. Furtherexamples of crosslinkers include those described in PCT/US/2004/040726.

Crosslinkers also include molecules comprising acrylate, allyl ormethacrylate groups. The acrylate, allyl or methacrylate crosslinkerscan be small molecules or polymeric in nature. In one embodiment, thelinker is selected from the group comprising poly (ethyleneglycol)-diacrylate (PEGDA), poly (ethylene glycol)-dimethacrylate(PEGDM), poly (ethylene glycol)-diacrylamide (PEGDAA) and poly (ethyleneglycol)-dimethacrylamide (PEGDMA), dextran acrylate, dextranmethacrylate, dextran glycidyl methacrylate, methacrylate functionalizedhyaluronic acid, acrylate functionalized hyaluronic acid, glyceroldimethacrylate, glycerol 1,3-diglycerolate diacrylate sorbitol acrylateand derivatives thereof.

The molecular weight of the crosslinker is typically less than that ofthe modified hyaluronic acid or other polymer as described above.Generally, the molecular weight of the crosslinker ranges from about 200to about 20,000 daltons. Additional exemplary molecular weight rangesfor the crosslinker are from about 1,000 to about 10,000 daltons (e.g.,having a molecular weight of about 1 kD, 2 kD, 3 kD, 4 kD, 5 kD, 6 kD, 7kD, 8 kD, 9 kD, or 10 kD, where kD equals kilodalton) or even from about1,000 to 5,000 daltons. Exemplary molecular weights for a crosslinkersuch as PEG dithiol, or any of the other suitable crosslinkers describedabove, include about 3350, 3400, and 5000 daltons, among others.

Bioactive Agents

The hydrogels, hydrogel precursors, and related compositions and/or kitsprovided herein may optionally comprise a bioactive agent. Bioactiveagents that may be included in the compositions and combinationsprovided herein include antimicrobials, antibiotics, analgesics,antibiotics, antiproliferative/antimitotic agents including naturalproducts such as vinca alkaloids (e.g. vinblastine, vincristine, andvinorelbine), paclitaxel, epidipodophyllotoxins (e.g. etoposide,teniposide), antibiotics (dactinomycin (actinomycin D) daunorubicin,doxorubicin and idarubicin), anthracyclines, mitoxantrone, bleomycins,plicamycin (mithramycin) and mitomycin, enzymes (L-asparaginase);antiproliferative/antimitotic alkylating agents such as nitrogenmustards (mechlorethamine, cyclophosphamide and analogs, melphalan,chlorambucil), ethylenimines and methylmelamines (hexamethylmelamine andthiotepa), alkyl sulfonates-busulfan, nitrosoureas (carmustine (BCNU)and analogs, streptozocin), trazenes-dacarbazinine (DTIC);antiproliferative/antimitotic antimetabolites such as folic acid analogs(methotrexate), pyrimidine analogs (fluorouracil, floxuridine, andcytarabine), purine analogs and related inhibitors (mercaptopurine,thioguanine, pentostatin and 2-chlorodeoxyadenosine [cladribine]);platinum coordination complexes (cisplatin, carboplatin), procarbazine,hydroxyurea, mitotane, aminoglutethimide; hormones (e.g. estrogen);anticoagulants (heparin, synthetic heparin salts and other inhibitors ofthrombin); fibrinolytic agents (such as tissue plasminogen activator,streptokinase and urokinase), aspirin, dipyridamole, ticlopidine,clopidogrel, abciximab; antimigratory agents; antisecretory agents (suchas brefeldin A); anti-inflammatory agents such as adrenocorticalsteroids (hydrocortisone, hydrocortisone acetate, cortisone acetate,tixocortol pivalate, prednisolone, methylprednisolone, prednisone,triamcinolone acetonide (or any other pharmaceutically acceptable saltsof triamcinolone), triamcinolone alcohol, mometasone, amcinonide,budesonide, desonide, fluocinonide, fluocinolone acetonide, halcinonide,betamethasone, betamethasone sodium phosphate, dexamethasone,dexamethasone sodium phosphate, and fluocortolone,hydrocortisone-17-butyrate, hydrocortisone-17-valerate, aclometasonedipropionate, betamethasone valerate, betamethasone dipropionate,prednicarbate, clobetasone-17-butyrate, clobetasol-17-propionate,fluocortolone caproate, fluocortolone pivalate, and fluprednideneacetate. Beclomethasone dipropionate monohydrate, flunisolide,fluticasone propionate, mometasone furoate monohydrate, triamcinoloneacetonide, fluticasone, furoate, non-steroidal agents (salicylic acidderivatives e.g. aspirin); para-aminophenol derivatives, i.e.acetaminophen; indole and indene acetic acids (indomethacin, sulindac,and etodolac), heteroaryl acetic acids (tolmetin, diclofenac, andketorolac), arylpropionic acids (ibuprofen and derivatives), anthranilicacids (mefenamic acid and meclofenamic acid), enolic acids (piroxicam,tenoxicam, phenylbutazone, and oxyphenthatrazone), nabumetone, goldcompounds (auranofin, aurothioglucose, gold sodium thiomalate);immunosuppressive (cyclosporine, tacrolimus (FK-506), sirolimus(rapamycin), azathioprine, mycophenolate mofetil); mitogenic ormorphogenic growth factor proteins, peptides or mimetics; vascularendothelial growth factor (VEGF), fibroblast growth factor (FGF),transforming growth factor-β(TGF-β) superfamily members includingTGF-β′s and bone morphogenic proteins (BMP's) such as BMP-2, 3, 4, 5, 6,7, 8; insulin and insulin-like growth factors (IGF's), hepatocyte growthfactor (HGF), epidermal growth factors (EGF's), Hedgehog proteins (SHHand IHH), activins, inhibins, demineralized bone (DBM) andplatelet-derived growth factors (PDGF's), hematopoietic growth factors(G-CSF, CSF-1, GM-CSF, erythropoietin, cytokines and lymphokinesincluding the interleukin family (IL-1 to 34)), interferons, nervegrowth factors (NGF's), neutralizing, antagonist or agonist antibodies,growth factor receptor agonists or antagonists, nitric oxide donors;anti-sense oligonucleotides, transcription factors, signaling cascademediators, and combinations thereof.

Antibiotics include antibiotics of the lincomycin family (referring to aclass of antibiotic agents originally recovered from streptomyceslincolnensis); antibiotics of the tetracycline family (referring to aclass of antibiotic agents originally recovered from streptomycesaureofaciens); sulfur-based antibiotics such as the sulfonamides; and soforth. Exemplary antibiotics of the lincomycin family include lincomycinitself(6,8-dideoxy-6-[[(1-methyl-4-propyl-2-pyrrolidinyl)-carbonyl]amino-]-1-thio-L-threo-□-D-galacto-octopyranoside),clindamycin, the 7-deoxy, 7-chloro derivative of lincomycin (e.g.,7-chloro-6,7,8-trideoxy-6-[[(1-methyl-4-propyl-2-pyrrolidinyl)carbonyl]amino]-1-thio-L-threo-□-D-galacto-octopyranoside), andpharmacologically acceptable salts and esters thereof. Exemplaryantibiotics of the tetracycline family include tetracycline itself4-(dimethylamino)-1,4,4α,5,5α,6,11,12α-octahydro-3,6,12,12α-pentahydroxy-6-methyl-1,11-dioxo-2-naphthacenecarboxamide),chlortetracycline, oxytetracycline, tetracycline, demeclocycline,rolitetracycline, methacycline and doxycycline and theirpharmaceutically acceptable salts and esters, particularly acid additionsalts such as the hydrochloride salt. Exemplary sulfur-based antibioticsinclude, but are not limited to, the sulfonamides sulfacetamide,sulfabenzamide, sulfadiazine, sulfadoxine, sulfamerazine,sulfamethazine, sulfamethizole, sulfamethoxazole, and pharmacologicallyacceptable salts and esters thereof, e.g., sulfacetamide sodium.Antimicrobials and/or antibiotics further include compounds such aserythromycin, bacitracin, neomycin, penicillin, polymyxin B,tetracyclines, viomycin, chloromycetin and streptomycins, cefazolin,ampicillin, azactam, tobramycin, clindamycin and gentamycin.

Analgesics include compounds such as lidocaine, benzocaine, andmarcaine.

A hydrogel as provided herein may also include living cells. Exemplaryliving cells include stem cells, parenchimal stem cells, blood-derivedcells, and bone marrow cells.

In one preferred embodiment, the hydrogel comprises a corticosteroid.Examples of suitable corticosteroids include hydrocortisone,hydrocortisone acetate, cortisone acetate, tixocortol pivalate,prednisolone, methylprednisolone, prednisone, triamcinolone,triamcinolone salts such as triamcinolone acetonide, triamcinolonebenetonide, triamcinolone furetonide, triamcinolone hexacetonide,triamcinolone diacetate, triamcinolone alcohol, mometasone, amcinonide,budesonide, desonide, fluocinonide, fluocinolone acetonide, halcinonide,betamethasone, betamethasone sodium phosphate, dexamethasone,dexamethasone sodium phosphate, fluocortolone,hydrocortisone-17-butyrate, hydrocortisone-17-valerate, aclometasonedipropionate, betamethasone valerate, betamethasone dipropionate,prednicarbate, clobetasone-17-butyrate, clobetasol-17-propionate,fluocortolone caproate, fluocortolone pivalate, fluprednidene acetate,beclomethasone dipropionate monohydrate, flunisolide, fluticasonepropionate, mometasone furoate monohydrate, and fluticasone furoate.

One preferred compound for use in a hydrogel formulation as providedherein is triamcinolone(11β,16α)-9-fluoro-11,16,17,21-tetrahydroxypregna-1,4-diene-3,20-dione),or a pharmaceutically acceptable salt or solvate thereof. The structureof triamcinolone acetonide is shown below.

The bioactive agent will typically be admixed, suspended in, orentrapped within a hydrogel as provided herein. Alternatively, thebioactive agent may be in the form of a polymer conjugate, or, may becovalently attached, in a releasable fashion, to a component used toprepare the hydrogel, e.g., the modified hyaluronic acid or crosslinker.

Hydrogels

The hydrogels provided herein are typically formed by reacting amodified hyaluronic acid or other suitable polymer as described abovewith a crosslinking agent (also described above) under conditionseffective to form a gel. Generally, the relative amounts of reagents andreactive groups, along with reaction conditions, are adjusted to provideoptimal reaction. Gel formation is carried out under mild and controlledconditions. Preferably, the resulting hydrogel contains less than twentypercent of combined unreacted functional groups contained within themodified hyaluronic acid and the crosslinker starting materials, morepreferably 5% or less of unreacted functional groups contained withinthe modified hyaluronic acid and the crosslinker starting materials, orideally, essentially no detectable amounts of unreacted functionalgroups such as unreacted vinyl sulfone or thiol groups. Such low levelsof unreacted functional groups in the resulting gel material arebeneficial in terms of providing a gel material having lowpro-inflammatory properties when administered in vivo, e.g., into ajoint. In a particular embodiment, a hydrogel formed by reaction of(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid with a thiolcrosslinker contains less than ten percent of unreacted thiol and vinylsulfone groups. The number of unreacted functional groups is controlledby careful monitoring of reaction conditions, adjustment of reactantratios, and knowledge of the degree of modification of the hyaluronicacid starting material.

Hydrogels thus formed will typically contain a percent by weight (wt/wt)of polymer to water (POLY/HOH) ranging from about 0.5 to 5.0 percent oreven more. Illustrative percents by weight of polymer to water for theresulting hydrogel are, in one or more embodiments, selected from 0.5,1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5 percent.

Formation of the lightly crosslinked hydrogels provided herein is due atleast in part to the low level of modification in themodified-hyaluronic acid starting material. For instance, the degree ofmodification of hyaluronic acid by reaction with divinyl sulfone can becontrolled by appropriate adjustment of reaction times as shown inExample 6. For example, in order to maintain a degree of modificationbelow about 20%, the reaction time under ambient conditions (e.g., from20-25° C.) is generally kept under about 3 minutes to form2-(vinylsulfonyl)ethoxy)_(1-20%)hyaluronic acid. The reaction ispreferably conducted using a molar excess of divinyl sulfone or otherappropriate modification reactant, such as a difunctional or greateracrylate or methyacylate reagent. As can be seen from the results inExample 6, and as would be expected, shorter reactions times result inlower degrees of modification of the starting polymer, e.g., hyaluronicacid. For example, under ambient conditions, a very short reaction time,i.e., on the order of seconds, resulted in vinyl-sulfone modifiedhyaluronic acid having about 4% substitution of vinyl sulfone groups,while a reaction time of one minute resulted in 8% vinylsulfone-substituted hyaluronic acid. See Table 1 for illustrativereaction times and conditions and the resulting degrees of substitutionof polymer obtained. In one embodiment, the reaction conditions areadjusted to result in vinylsulfone-substituted hyaluronic acid havingfrom about 1% to about 10% substitution. In a related embodiment, themodification reaction is carried out under ambient conditions for about10 seconds to about 120 seconds. The modification reaction, e.g.,reaction of hyaluronic acid and divinyl sulfone, can be carried outunder basic conditions, e.g., in aqueous base such as aqueous sodiumhydroxide, aqueous potassium hydroxide, or using any other suitable basethat is soluble in water, followed by quenching of the reaction byaddition of acid, such as hydrochloric acid, sulfuric acid, phosphoricacid, or the like. Generally, acid is added at such time and in anamount sufficient to adjust the pH down to a range from about 4 to 6.5or so, to quench the reaction to thereby achieve a desired degree offunctional group modification of the parent polymer. The product maythen be optionally purified, e.g., by dialysis, and optionally driedsuch as by lyophilization.

The hydrogel precursor composition is then lightly cross-linked,optionally in the presence of a cross-linking agent if necessary. Forexample, a vinyl-sulfone modified hyaluronic acid such as2-(vinylsulfonyl)ethoxy)_(1-20%)hyaluronic acid, or2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid, such as describedabove, is reacted with a suitable crosslinker such as athiol-functionalized PEG reagent such as PEG-dithiol or otherappropriate crosslinking agent as described above under reactionconditions effective to form a crosslinked hydrogel. In a preferredembodiment, the crosslinking reaction is carried out in aqueoussolution, e.g., under physiological conditions. In one embodiment, thereaction is carried out in saline solution. See, e.g., Examples 2, 3, 4,and 5. The volume ratios of reactants can be adjusted according to thedesired properties of the resulting hydrogel, and will depend upon theconcentrations of the reactant solutions, the particular molecularweights and structures of the reactants, and the like. For instance,illustrative relative molar ratios of functional group to crosslinkerinclude the following, where, e.g., an exemplary functional group isvinyl sulfone as contained in the vinyl-sulfone modified hyaluronic acidand relative amount of crosslinker refers to crosslinker itself, forexample, the crosslinker molecule rather than the number of reactivegroups such as thiol groups contained in a crosslinker molecule such asin PEG-dithiol: from about 1 to 2.5, or from about 1.25 to 2.0, or fromabout 1.3 to about 1.8. Alternatively, the crosslinker may be added as asolid to a solution of the modified hyaluronic acid. In an instance inwhich a sterile formulation is desired, the crosslinker is sterilizedprior to addition, e.g., by electron-beam treatment. The crosslinkingreaction is typically carried out under mild reaction conditions, e.g.,at temperatures ranging from about 20° C. to about 45° C., e.g., at anyone of the following temperatures: 20° C., 21° C., 22° C., 23° C., 24°C., 25° C., 26° C., 27° C., 28° C., 29° C., 30° C., 31° C., 32° C., 33°C., 34° C., 35° C., 36° C., 37° C., 38° C., 39° C., 40° C., 41° C., 42°C., 43° C., 44° C., or 45° C. Following mixing or reacting of themodified hyaluronic acid and crosslinker reactants, and any otheroptional reactant components, the resulting composition is typicallyallowed to react, e.g., in an incubator, for a period of time suitableto result in formation of a gel. Depending on the reaction temperature,the reactants are typically allowed to react for a period of about 8 toabout 36 hours, or from about 10 to about 24 hours, or for about 12 toabout 18 hours.

The crosslinking reaction may be carried out under sterile conditions,i.e., using sterile reactants and under sterile conditions as describedgenerally in the accompanying examples, to provide a sterile hydrogel.For instance, all solution components may be sterile filtered prior toreaction to thereby form a sterile composition.

Additional exemplary lightly crosslinked hydrogels are formed, e.g., bycross-linking of thiol-modified hyaluronic acid materials such asCarb-S™. Carb-S™ is produced by carboxymethylation of hyaluronic acid,followed by reaction with 3,3′dithiobis(propanoic dihydrazide), DTPH, inthe presence of a coupling agent, followed by reduction of the disulfidegroups with a reagent such as dithiothreitol. See, e.g., U.S. PatentPublication No. US2008-002595. Additional thiol-modified hyaluronic acidmaterials are described in U.S. Patent Publication No. US2009-0105093;an illustrative material described in the foregoing publication is ahyaluronic acid derivatized by reaction with a thiol-containinghydrazide reactant. The hydrogel may also be formed from athiol-modified hyaluronic acid material as described in U.S. Pat. No.6,884,788. In a preferred embodiment, the foregoing thiol-modifiedhyaluronic acid materials are prepared using the synthetic approachesdescribed, with the exception that the degree of modification of thehyaluronic starting material is low, such that less than about 20% oreven more preferably, less than about 10% of the hyaluronic acidhydroxyl groups are chemically modified. Such thiol-derivatizedhyaluronic acid materials can be lightly self-crosslinked, due to theability of thiols to self-react. Alternatively, the lightly cross-linkedhydrogel may be formed by reaction with a cross-linking agent such as aPEG-acrylate.

In one or more particular embodiments, the crosslinked hydrogelcomposition contains an active agent. Preferred classes of bioactiveagents include steroids, growth factors, anti-proliferative agents, andantibiotics. One particularly advantageous class of active agent forincorporation into the instant hydrogels are the corticosteroids.Illustrative corticosteroids include but are not limited to thefollowing: triamcinolone, triamcinolone salts such as triamcinoloneacetonide, triamcinolone hexacetonide, triamcinolone benetonide,triamcinolone furetonide, and triamcinolone diacetate and the like, andmethylprednisolone. Generally, the resultant hydrogel contains fromabout 0.01% by weight to about 20% by weight bioactive, depending on itspotency. Illustrative amounts of bioactive agent contained in thehydrogel (based on overall wet gel weight) are from about 10% to about20% by weight, e.g., for a less potent bioactive agent, and from about0.01% to about 10% by weight, or from about 0.01% to about 5%, or fromabout 0.01% to about 3%, or from about 0.1 to about 2% bioactive agent,or even from about 0.1 to about 1% bioactive agent, e.g., for a morepotent bioactive agent such as triamcinolone acetonide. In certainembodiments, the hydrogel is used for delivering a poorly water solublebioactive agent by incorporating such bioactive agent in the hydrogel.

Advantageously, the present hydrogels are formed both under mildreaction conditions and can be formed in the absence of a polymerizationinitiator. Moreover, sufficient gellation occurs in the absence of theapplication of an external energy source. For example, the gel-formationreaction can be carried out at a temperature ranging from about 20° C.to 45° C.—and in the absence of initiators and accelerants.Additionally, the gelation, i.e., hydrogel formation, occurs without therelease of any small molecule chemical by-products. Thus, the hydrogelsprovided herein contain a minimal number of additives or contaminantsthat could potentially lead to a pro-inflammatory response upon in-vivoadministration.

Sterile hydrogels can be formed under sterile conditions, e.g., byplacing aqueous solutions of each of the modified hyaluronic acid andcrosslinker into a sterile syringe and or centrifuge tube, followed bythorough mixing. Typically the mixed reactants (i.e, modified hyaluronicacid and crosslinker) are placed in an incubator set at an appropriatetemperature (e.g., ranging from about 20° C. to 45° C.) until thematerial forms a gel. See, e.g., Example 2, 18, 21, 22, 23, 24, 25, 27,28, 29 and 30 for representative preparations of hydrogel formulations,including exemplary volume ratios of reactants.

Additional unmodified hyaluronic acid, typically in the form of anaqueous solution or mixture, may optionally be added to either the gelprecursor formulation, prior to gel formation, or after gel formation(e.g., to a gel slurry), to provide a composition comprising crosslinkedhydrogel particles in an aqueous solution of hyaluronic acid. See, e.g.,Example 8. The average molecular weight of the hyaluronic acid (i.e.,unmodified hyaluronic acid) in the solution typically ranges from about750,000 to about 1,200,000 daltons or even higher. A preferred aqueoussolution is a saline solution of hyaluronic acid, where exemplaryaqueous solutions of hyaluronic acid added to the hydrogel haveconcentrations ranging from about 0.3% to about 4%, or from about 0.5%to about 2% by weight. One representative formulation comprises thefollowing relative amounts of components: 4 mL of gel slurry((2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid/PEG-dithiol) with 2 mLof hyaluronic acid at a concentration of 20 mg/mL. A particularlypreferred formulation comprises 4 mL of gel slurry((2-(vinylsulfonyl)ethoxy)_(4%)hyaluronic acid/PEG-dithiol) with 2 mL ofhyaluronic acid at a concentration of 20 mg/mL. Typically, the finalhyaluronic acid content in the resulting swollen gel ranges from about0.05 to 5 percent (0.5 mg/mL to 50 mg/mL). Preferably, the finalhyaluronic acid content in the resulting swollen gel is from about 0.1to 3 percent, or from about 0.1 to 1 percent, or from about 0.5-0.8%.Illustrative final hyaluronic acid content in the resulting swollen gelmay, for example, correspond to any of the following percentages: 0.1,0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, and 5.0. Forexample, representative relative amounts (weight ratios) of hyaluronicacid to crosslinked (e.g., (2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronicacid/PEG-dithiol) hydrogel particles in the resultant compositiontypically fall within a range from about 10:1, or from about 5:1, orfrom about 3:1, or from about 1:1. The resulting composition may alsooptionally contain one or more surfactants. Illustrative surfactantsinclude sodium carboxymethylcellulose, polysorbate 80, Tween 80,polyethylene glycol (e.g., PEG 3350), and the like.

If desired, a bioactive agent may be added to the reaction mixture priorto crosslinking or alternatively, added to the crosslinked gel afterformation. Examples 9-16 demonstrate hydrogel formation, as well asincorporation and subsequent sustained release of a bioactive agent,triamcinolone acetonide, from representative hydrogel compositions.Alternatively, living cells such as stem cells, parenchimal stem cells,blood derived cells, and bone marrow cells can be incorporated into thesubject hydrogels.

For the subject hydrogels, with or without a bioactive agent, thehydrogel can be dispersed in a solution of one or more polyanionicpolysaccharides (PAS) as described above. Non-exclusive examples ofpolyanionic polysaccharides include, for example, in addition tohyaluronic acid (HA), carboxymethylcellulose (CMC), carboxymethylamylose(CMA), chondroitin-4-sulfate, chondroitin-6-sulfate, dermatan sulfate,dermatin-6-sulfate, heparin sulfate, heparin, keratin sulfate and theirderivatives, and combinations thereof. Such polymers are known in theart, and described, for example, in U.S. Pat. No. 6,056,970. Othersolutions of polymers that the subject hydrogels can be dispersed ininclude fibrin, fibrinogen, starch, poly(amino acids); peptides,proteins, gelatin, collagen and poly(ethylene glycol). A solutioncontaining one or more combinations of the above polymers can be used todisperse the subject hydrogel particles. The polymer solutions can beprepared in a concentration range from at least 0.1 mg/mL to the maximumwater or 0.9% saline solubility. As described previously, one preferredpolymer is hyaluronic acid having a molecular weight between about500,000 and 3 million at a concentration range of about 10 mg/mL toabout 25 mg/mL. The combination of polymer solution and hydrogel can bemanufactured under aseptic conditions such that the final packagedcombination is sterile.

As described in Example 8, the subject hydrogels can be mixed indifferent ratios with the selected polymer solution. Volume ratios ofmixing the subject hydrogel and the polymer solution can include but arenot limited to about 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1,2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1. The preferred volumeratios of mixing the subject hydrogel and the polymer solution are about3:1, 2:1 and 1:1.

The pH of the subject hydrogels and subject hydrogel/polymer solutiondispersions can be modified by the addition of buffers, acid and bases.The preferred pH range for the subject hydrogels and subjecthydrogel/polymer solution dispersions is from about 5-8 and morepreferably from about 6-7.6.

The ionic strength of the subject hydrogels and subject hydrogel/polymersolution dispersions can be modified by the addition of salts. Onepreferred salt used to modify the ionic strength of the subjecthydrogels and subject hydrogel/polymer solution dispersions is sodiumchloride. A preferred final ionic strength of the subject hydrogels andsubject hydrogel/polymer solution dispersions is selected such that thesubject hydrogels and subject hydrogel/polymer solution dispersions areabout isotonic.

Pharmaceutically acceptable preservatives may also be added to thesubject hydrogels and subject hydrogel/polymer solution dispersions.These can include agents such as sodium benzoate or benzyl alcohol.

The subject hydrogels and subject hydrogel/polymer solution dispersionsmay, in certain embodiments, be packaged in a syringe. The syringe canbe made from plastic (e.g. polypropylene, polycarbonate, polystyrene) orglass or any other pharmaceutically acceptable material. The volume ofthe subject hydrogels and subject hydrogel/polymer solution dispersionscontained within the syringe may range from 0.5 mL to 20 mL withpreferable volumes being 1 mL, 2 mL, 3 mL, 4 mL, 5 mL, 6 mL and 7 mL.

The resulting hydrogel material may be processed into particles having asize ranging from about 0.10 to 3.0 millimeters (See, e.g., Examples 3and 4), or may be in the form of an aqueous gel slurry. For example,gelled material can be broken up into pieces, mixed with saline, andallowed to swell. Appropriately sized particles can then be formed fromthe gel material by extrusion through a mesh having the desired screensize, e.g., from about 0.10 to 3.0 millimeters. The resulting particles,when placed in an aqueous medium, form a gel slurry. In one embodiment,the gel is packaged in a syringe suitable for use with a 18-21 gaugeneedle, such that the hydrogel can be injected, i.e., into anintra-articular space. Generally, the volume of hydrogel compositioninjected into an intra-articular space of a subject ranges from about0.5 to about 8 mL, preferably from about 3 to 6 mL, or even from about4-6 mL.

As illustrated in the accompanying Examples, the hydrogels can beprovided as sterile compositions.

As described above, and in the Examples, the hydrogels may be providedin a sealed container such as a syringe (which can be capped, optionallywith a vented cap). The syringe may then be placed in a container, suchas a foil pouch which is then sealed. The pouch may be vacuum sealed,sealed under an inert gas such as nitrogen or argon, or sealed followingone or more vacuum/back fill cycles where the back fill gas is an inertgas such as nitrogen or argon. For the pouch sealed under one or morevacuum/back fill cycles, the cycle can be adjusted such that the pouchis finally sealed under either vacuum or an inert gas. The pouch mayoptionally contain a dessicant and/or an oxygen scavenger.

Uses

The gel compositions described herein advantageously exhibit reducedundesirable side effects on the cartilage in comparison to commerciallyavailable viscosupplements and, in embodiments in which the hydrogelfurther comprises a bioactive agent, exhibit reduced undesirable sideeffects on the cartilage when compared to administration of anequivalent amount of active agent absent hydrogel incorporation. The gelcompositions provided herein possess extremely low pro-inflammatoryproperties as illustrated in Example 17 and in FIGS. 4-8, amongst havingother beneficial features.

The hyaluronic acid polymer compositions described herein may be used ininjectable or implantable formulations, for use, e.g., embryonicdevelopment, tissue organization, wound healing, angiogenesis andtumorigenesis. See D. D. Allison and K. J. Grande-Allen, TissueEngineering, Vol. 12, Number 8, 2131-2140 (2006); G. D. Prestwich et al,Tissue Engineering, Vol. 12, Number 8, 2171-2180 (2006); G. D. Prestwichet al, Tissue Engineering, Vol. 12, Number 12, 3405-3416 (2006).Hydrogel compositions comprising a corticosteroid such as triamcinoloneacetonide are useful for providing relief of pain experienced by asubject. Injection of a therapeutically effective amount of the hydrogelcomposition into an intra-articular space of a joint can be effective,e.g., for providing sustained relief of joint pain experienced by asubject. Ideally, a measurable degree of pain relief is initiallyexperienced by the subject from within about one hour to one weekpost-injection, or more preferably, from about one hour to about one daypost-injection. Typically, injection of the hydrogel results in a degreeof relief of pain lasting from about three to nine monthspost-injection. Depending upon the particular subject and condition tobe treated, a therapeutically effective dosage volume of hydrogeltypically ranges from about 0.5 mL to 20 mL, with exemplary volumesincluding 1 mL, 2 mL, 3 mL, 4 mL, 5 mL, 6 mL and 7 mL.

For example, the hydrogel compositions provided herein, optionallycontaining one or more bioactive agents, may be used as adhesivecompositions, e.g., as tissue adhesives and sealants that may be usedfor various applications, including preventing bleeding, covering openwounds, and other biomedical applications. These compositions may beused in, for example, apposing surgically incised or traumaticallylacerated tissues, retarding blood flow such as those from wounds,preventing restenosis or blood clotting, drug delivery; dressing burns,and aiding repair and regrowth of living tissue. The hyaluronicacid-based polymer composition as provided herein may be used forsupplementing or inducing and regenerating damaged organs or tissues ina mammalian subject, such as a human. The composition is decomposed orabsorbed, or alternatively, remains in the subject (e.g., mammaliansubject) without having adverse influences on subject when embedded orcontained therein.

The subject compositions may be used as tissue fillers, dermal fillers,bulking agents, and embolic agents as well as agents to repair cartilagedefects/injuries and agents to enhance bone repair and/or growth.

The subject compositions may also be used in the treatment ofosteoarthritis or rheumatoid arthritis, or for other inflammatoryarthritides such as gout or calcium pyrophosphate deposition disease(e.g., by injection into the intra-articular space of a joint), or inthe reduction or prevention of adhesions that can form following asurgical procedure. It has been discovered that the subject compositionsare useful for reducing the damage to cartilage upon injection of acorticosteroid by incorporation of the corticosteroid into a hydrogelmaterial as provided herein.

As one particular measure of the foregoing, i.e., when the hydrogelcomprises a corticosteroid incorporated therein, and the method iseffective to result in damage to the cartilage that is reduced from thecartilage damage that occurs upon administration of an equivalent amountof the corticosteroid absent hydrogel entrapment, such reduced damage tothe cartilage is characterized in a goat joint injection model by totalMankin score at 28 days post injection. See Example 34 for a descriptionof determination of total Mankin score. Additional indicators forassessing reduced cartilage damage are also available; such parametersand associated data are also provided in Example 34.

Several advantages are associated with the entrapment/incorporation ofsteroid particles within a hydrogel as provided herein, including one ormore of the following. For instance, the trapping of steroid particleswithin the instant hydrogels is effective to prevent direct contact ofthe majority of the steroid particles with the joint tissues. Moreover,the trapping of steroid particles in the instant hydrogels is effectiveto maximize the localized concentration of the steroid in the joint,while minimizing its systemic concentration. Additionally, theentrapment of steroid particles in the instant hydrogel formulations iseffective to protect the steroid particles from premature clearance fromthe joint. Finally, by entrapping the steroid in the hydrogel,therapeutic efficacy of the steroid is attained at a lower total dosethan would be attained absent hydrogel entrapment, while minimizingunwanted local and systemic side effects. See, for example, Examples14-16 along with FIGS. 2, 3, and 4, demonstrating linear release of drugfrom an exemplary hydrogel composition in a controlled and sustainedlinear fashion over time.

For hydrogel-based compositions comprising a bioactive agent, suchcompositions may be used as delivery systems for the treatment ofconditions such as osteoarthritis, sinusitis, allergic rhinitis andchronic rhinosinusitis, among others. Such compositions may also be usedas dermal fillers, agents to repair cartilage defects/injuries andagents to enhance bone repair and/or growth.

The present application will now be described in connection with certainembodiments, which are not intended to limit the scope of the invention.On the contrary, the present application covers all alternatives,modifications, and equivalents as included within the scope of theclaims. Thus, the following will illustrate the practice of the presentapplication, for the purposes of illustration of certain embodiments andis presented to provide what is believed to be a useful and readilyunderstood description of its procedures and conceptual aspects.

EXAMPLES

The following examples are put forth to provide those of ordinary skillin the art with a complete disclosure and description of how thecompounds, compositions, and methods provided herein are made andevaluated, and are intended to be purely exemplary. Thus, the examplesare in no way intended to limit the scope of what the inventors regardas their invention. There are numerous variations and combinations ofreaction conditions, e.g., component concentrations, desired solvents,solvent mixtures, temperatures, pressures, and other reaction parametersand conditions that may be employed to optimize product characteristicssuch as purity, yield, and the like. Such are considered as well withinthe scope of the present disclosure.

Example 1 Synthesis of Vinyl Sulfone Derivatized Hyaluronic Acid(HA-VS)—Low Degree of Modification

5 g hyaluronic acid (HA) [9.4×10⁴ cps (3% in water)] was weighed into a1 L round bottom flask. 500 mL sterile filtered water was added to theHA. The flask was placed on a rotary evaporator which was set to rotateat between 20-100 rpm. The solution was rotated until all the HA wasdissolved (approx. 16-18 hrs). The HA solution (10 mg/mL) was thentransferred to a 1 L glass beaker. A stirring paddle that was connectedto an overhead stirrer was inserted into the solution and was set to astirring speed that ensured efficient stirring of the solution. 333 mLof a 0.25 N NaOH solution (83.2 mL 1N NaOH added to 249.8 mL deionizedwater) was added to the stirring HA solution. After about 1 min, 150 mLof a divinyl sulfone solution (18 mL divinyl sulfone dissolved in 132 mLdeionized water) was added rapidly to the stirring solution. After 15seconds (as measured from the completion of the divinyl sulfone solutionaddition), the pH of the solution was adjusted to between 5 and 6 byrapidly adding approx. 14 mL 6N HCl. The reaction solution was thendialysed using a tangential flow filtration system (spectrapor system,cartridge P/N M6-100S-301-01P). The total volume was 11 times theoriginal solution volume. Once the purification step was completed, thesolution was concentrated to approx. 14-20 mg/mL. The vinyl sulfonefunctionalized HA (HA-VS) was removed from the TFF system and was placedin a plastic container which was then closed with a screw top lid. Asample of the HA-VS was removed, frozen at −80° C. and then lyophilized.The dried sample was sent for ¹H-NMR analysis.

Determination of Percentage Vinyl Sulfone Substitution for HA-VS

Approx. 15-17 mg of the dried sample was weighed into a tared 2 mL tube.The sample was reconstituted in 1.5 mL D₂O. The sample was transferredto an NMR tube. The ¹H-NMR (256 scans) of the sample was taken and thespectrum was printed out with the specific peaks in the 6.3-6.5 ppm (2peaks from the 2 CH₂=protons from the vinyl sulfone residue) and 1.5-2.5ppm (singlet from the 3 CH₃-protons from the N-acetyl group of the HA)regions being integrated. The percent modification is calculated asfollows:

${\%\mspace{14mu}{modification}} = {150 \times \frac{{Integral}\mspace{14mu}{vinyl}\mspace{14mu}{sulfone}\mspace{14mu}{peaks}}{{Integral}\mspace{14mu}{Acetamide}\mspace{14mu}{peak}}}$

The ¹H-NMR spectrum (FIG. 1) showed that the HA had a vinyl sulfonesubstitution level of approximately 4%, based upon an integration ofvinyl sulfone peaks relative to the acetamide methyl group of thehyaluronic acid.

A sample of the HA-VS was used to determine the dry weight which wasused to determine the specific concentration of the HA-VS solution. TheHA-VS concentration was 18 mg/mL.

Example 2 Synthesis of a Gel Prepared from Vinyl Sulfone ModifiedHyaluronic Acid (HA-VS) and PEG3400-Dithiol

A solution of HA-VS, prepared as described in Example 1, was dilutedusing deionized water to a concentration of 14 mg/mL. 11 mL of the HA-VSsolution was placed into a 20 mL sterile syringe. The HA-VS solution wasfiltered through a 0.2 μm sterile syringe filter into a sterile 50 mLcentrifuge tube. A 50 mg/mL solution of PEG-(SH)₂ [Laysan Bio Inc.,Item# SH-PEG-SH-3400-1 g] was prepared by dissolving 40.1 mg PEG-(SH)₂in 0.802 mL deionized water. The PEG-(SH)₂ solution was transferred to a1 mL sterile syringe and was filtered through a 0.2 μm sterile syringefilter. 10 mL of the sterile filtered HA-VS was transferred to a sterile50 mL centrifuge tube. 250 μL of a 0.5 M sodium phosphate solution(filtered through a 0.2 μm sterile syringe filter) was added to theHA-VS solution. The resultant solution was mixed thoroughly. 380 μL [19mg PEG-(SH)₂] of the sterile 50 mg/mL PEG-(SH)₂ solution was added tothe HA-VS solution. The resultant solution was mixed thoroughly. Theabove steps were performed in a biohood to maintain sterility. TheHA-VS/PEG-(SH)₂ solution was then placed in a 37° C. incubator for atleast 16 hours to promote gel formation. After at least 16 hours, theHA-VS/PEG-(SH)₂ solution had crosslinked to form a gel. The gelledmaterial was then removed from the incubator.

Example 3 Preparation of a HA-VS/PEG-(SH)₂ Gel Slurry—Single Extrusion

The HA-VS/PEG-(SH)₂ gel from Example 2 was physically broken into piecesusing a glass rod. The gel was transferred to a sterile 60 mL syringethat was capped with a syringe cap. 40 mL 0.9% sterile NaCl was added tothe gel. The plunger was inserted into the syringe barrel and thesyringe was inverted. The syringe cap was opened to release any pressureand was then closed. The syringe was inverted several times to ensuregood mixing of the saline and the gel pieces. The gel was allowed toswell overnight (at least 16 hrs).

A 23 mm diameter disc of a polyester mesh (McMaster Carr, Cat #9218T13,Mesh Size: 20.3×20.3, Square/Rectangle Size: 0.0331″, Micron Rating: 840Microns, Percentage of Open Area: 46, Thread Diameter: 0.0157″) was cutout using a 23 mm leather punch. The disc was inserted into a 25 mmsyringe filter holder (Cole Palmer, Cat # EW-29550-42) and the filterholder was closed. The filter holder that contained the mesh wasautoclaved. The syringe cap of the syringe was removed and the syringefilter containing the mesh was attached to the syringe. The gel wasextruded through the mesh into a sterile 50 mL centrifuge tube. Thecentrifuge tube was capped with a screw top lid. The resulting productis a slightly viscous slurry of the particles, where the particles donot really settle out but typically remain suspended. The above stepswere performed in a biohood.

Example 4 Preparation of a HA-VS/PEG-(SH)₂ Gel Slurry—Double Extrusion

The HA-VS/PEG-(SH)₂ gel from Example 2 was physically broken into piecesusing a glass rod. The gel was transferred to a sterile 60 mL syringethat was capped with a syringe cap. 40 mL 0.9% sterile NaCl was added tothe gel. The plunger was inserted into the syringe barrel and thesyringe was inverted. The syringe cap was opened to release any pressureand was then closed. The syringe was inverted several time to ensuregood mixing of the saline and the gel pieces. The gel was allowed toswell overnight (at least 16 hrs).

A 23 mm diameter disc of a polyester mesh (McMaster Carr, Cat #9218T13,Mesh Size: 20.3×20.3, Square/Rectangle Size: 0.0331″, Micron Rating: 840Microns, Percentage of Open Area: 46, Thread Diameter: 0.0157″) was cutout using a 23 mm leather punch. The disc was inserted into a 25 mmsyringe filter holder (Cole Palmer, Cat # EW-29550-42) and the filterholder was closed. The filter holder that contained the mesh wasautoclaved. The syringe cap of the syringe was removed and the syringefilter containing the mesh was attached to the syringe. The gel wasextruded through the mesh into a sterile 50 mL centrifuge tube. Theextruded gel was then put into a sterile 60 mL syringe and the syringefilter that contained the mesh was attached to the syringe. The gel wasextruded through the through the mesh into a sterile 50 mL centrifugetube. The centrifuge tube was capped with a screw top lid. The abovesteps were performed in a biohood.

Example 5 Preparation of Syringes Loaded with HA-VS/PEG-(SH)₂ Gel Slurry

5 mL of the prepared HA-VS/PEG-(SH)₂ gel slurry (from Example 3 orExample 4) was transferred into a sterile 10 mL glass syringe (B&D) thathad a syringe cap applied. A sterile stopper was inserted into the topof the syringe. A plunger rod was screwed into the stopper. The syringewas inverted and once the gel slurry had reached the stopper, thesyringe cap was loosened slightly and the plunger was depressed untilthe majority of the air in the syringe was removed. The syringe cap wastightened. The above steps were performed in a biohood.

Example 6 Synthesis of Vinyl Sulfone-Derivatized Hyaluronic Acid

HA-VS compositions having different degrees of substitution wereprepared using the method described in Example 1, with the exceptionthat reaction times were increased. By increasing the reaction time, agreater degree of vinyl sulfone substitution was obtained. The resultsof these reactions are shown in the table below:

TABLE 1 REACTION DEGREE OF SUBSTITUTION TIME FOR VS MODIFIED HA 15 sec 4% 1 minute  8% 3 minutes 20% 5 minutes 26% 25 minutes 29%

Example 7 Synthesis of HA-VS/PEG-(SH)₂ Gel

The HA-VS samples having varying levels of vinyl sulfone substitution(Example 6) were used to prepare HA-VS/PEG-(SH)₂ gels using the methodand reagent ratios described in Example 2. Each of the startingmaterials formed a gel upon reaction with PEG-dithiol.

Example 8 Preparation of HA-VS/PEG-(SH)₂ Gel Slurry with Hyaluronic Acid

2 g hyaluronic acid [9.4×10⁴ cps (3% in water)] was weighed into a 250mL round bottom flask. 100 mL sterile saline was added to the hyaluronicacid in the flask. The flask was attached to a rotary evaporator (Buchi)and was rotated at 50 rpm for at least 16 hrs to form a 2% hyaluronicacid solution. The following series of steps were performed in abiohood. The hyaluronic acid solution was filtered through a 0.2 umsterile filter. Using the HAVS/PEG-(SH)2 gel slurry (as prepared inExample 3 or 4), a series of formulations were prepared in which theprepared HA-VS/PEG-(SH)2 gel slurry was mixed with hyaluronic acid. Thevolumes of the hyaluronic acid solution and the HA-VS/PEG(SH)₂ gelslurry used to prepare these formulations are shown in the table below:

TABLE 2 VOLUME HYALURONIC VOLUME HA-VS/PEG- FORMULATION ACID (ML) (SH)₂GEL SLURRY (ML) 1 1 5 (single extrusion slurry) 2 2 4 (single extrusionslurry) 3 3 3 (single extrusion slurry) 4 4 2 (single extrusion slurry)5 5 1 (single extrusion slurry) 6 1 5 (double extrusion slurry) 7 2 4(double extrusion slurry) 8 3 3 (double extrusion slurry) 9 4 2 (doubleextrusion slurry) 10 5 1 (double extrusion slurry)

The indicated volumes of hyaluronic acid solution and HA-VS/PEG-(SH)2gel slurry, as identified in the table above, were added to a 15 mLsterile centrifuge tube. The cap was placed on the tube and the tube wasinverted back and forth until the components were well mixed. Eachformulation was then transferred into a 10 mL glass syringe that had asyringe cap after which the plunger was inserted and the excess air wasexpelled. The syringe cap was then tightened.

Example 9 Synthesis of HA-VS-PEG-(SH)₂ Gel Containing TriamcinoloneAcetonide

A solution of the HA-VS, prepared as in Example 1, was diluted usingdeionized water to a concentration of 14 mg/mL. 11 mL HA-VS solution wasplaced into a 20 mL sterile syringe. The HA-VS solution was filteredthrough a 0.2 um sterile syringe filter into a sterile 50 mL centrifugetube. A 50 mg/mL solution of PEG-(SH)₂ was prepared by dissolving 40.1mg PEG3400-(SH)₂ in 0.802 mL deionized water. The PEG-(SH)₂ solution wastransferred to a 1 mL sterile syringe and was filtered through a 0.2 umsterile syringe filter. 10 mL of the sterile filtered HA-VS wastransferred to a sterile 50 mL centrifuge tube. 100 mg of triamcinoloneacetonide (Spectrum Chemicals, U.S.P grade, micronized) was added to theHAVS solution. The cap of the centrifuge tube was placed on the tube andthe solution was inverted back and forth until the triamcinoloneacetonide was homogeneously mixed with the HA-VS. 250 μL of a sterilefiltered (0.2 um sterile filter) 0.5 M sodium phosphate solution wasadded to the HA-VS solution. The resultant solution was mixedthoroughly. 380 μL of the sterile 50 mg/mL PEG-(SH)₂ solution was addedto the HA-VS solution. The resultant solution was mixed thoroughly. Theabove steps were performed in a biohood. The HA-VS/PEG-(SH)₂ solutionwas then placed in a 37° C. incubator for at least 16 hours. At thisstage the HA-VS/PEG(SH)₂ solution had crosslinked to form a gel. Thegelled material was then removed from the incubator. The resulting gelcontains approximately 0.2% triamcinolone acetonide.

The above procedure was also carried out as set forth above with theexception that 20 mg of triamcinolone acetonide (Spectrum Chemicals,U.S.P grade, micronized) was added to the HA-VS solution.

Example 10 Preparation of HA-VS-PEG-(SH)₂ Gel Slurry ContainingTriamcinolone Acetonide: Single Extrusion

The triamcinolone acetonide-containing HA-VS/PEG-(SH)₂ gel (Example 9)was physically broken into pieces using a glass rod. The gel wastransferred to a sterile 60 mL syringe that was capped with a syringecap. 40 mL 0.9% sterile NaCl was added to the gel. The plunger wasinserted into the syringe barrel and the syringe was inverted. Thesyringe cap was opened to release any pressure and was then closed. Thesyringe was inverted several time to ensure good mixing of the salineand the gel pieces. The gel was allowed to swell overnight (at least 16hrs).

A 23 mm diameter disc of a polyester mesh (McMaster Carr, Cat #9218T13,Mesh Size: 20.3×20.3, Square/Rectangle Size: 0.0331″, Micron Rating: 840Microns, Percentage of Open Area: 46, Thread Diameter: 0.0157″) was cutout using a 23 mm leather punch. The disc was inserted into a 25 mmsyringe filter holder (Cole Palmer, Cat # EW-29550-42) and the filterholder was closed. The filter holder that contained the mesh wasautoclaved. The syringe cap of the syringe was removed and the syringefilter containing the mesh was attached to the syringe. The gel wasextruded through the mesh into a sterile 50 mL centrifuge tube. Thecentrifuge tube was capped with a screw top lid. The above steps wereperformed in a biohood.

Example 11 Preparation of HA-VS-PEG-(SH)₂ Gel Slurry ContainingTriamcinolone Acetonide: Double Extrusion

The triamcinolone acetonide-containing HA-VS/PEG-(SH)₂ gel (Example 9)was physically broken into pieces using a glass rod. The gel wastransferred to a sterile 60 mL syringe that was capped with a syringecap. 40 mL 0.9% sterile NaCl was added to the gel. The plunger wasinserted into the syringe barrel and the syringe was inverted. Thesyringe cap was opened to release any pressure and was then closed. Thesyringe was inverted several times to ensure good mixing of the salineand the gel pieces. The gel was allowed to swell overnight (at least 16hrs).

A 23 mm diameter disc of a polyester mesh (McMaster Carr, Cat #9218T13,Mesh Size: 20.3×20.3, Square/Rectangle Size: 0.0331″, Micron Rating: 840Microns, Percentage of Open Area: 46, Thread Diameter: 0.0157″) was cutout using a 23 mm leather punch. The disc was inserted into a 25 mmsyringe filter holder (Cole Palmer, Cat # EW-29550-42) and the filterholder was closed. The filter holder that contained the mesh wasautoclaved. The syringe cap of the syringe was removed and the syringefilter containing the mesh was attached to the syringe. The gel wasextruded through the mesh into a sterile 50 mL centrifuge tube. Theextruded gel was then put into a sterile 60 mL syringe and the syringefilter that contained the mesh was attached to the syringe. The gel wasextruded through the through the mesh into a sterile 50 mL centrifugetube. The centrifuge tube was capped with a screw top lid. The abovesteps were performed in a biohood.

Example 12 Preparation of Syringes Containing Triamcinolone AcetonideGel Slurry

5 mL of the prepared triamcinolone acetonide-containing HA-VS/PEG(SH)₂gel slurry (Example 10 or Example 11) was transferred into a sterile 10mL glass syringe (B&D) that had a syringe cap applied. A sterile stopperwas inserted into the top of the syringe. A plunger rod was screwed intothe stopper. The syringe was inverted and once the gel slurry hadreached the stopper, the syringe cap was loosened slightly and theplunger was depressed until the majority of the air in the syringe wasremoved. The syringe cap was tightened. The above steps were performedin a biohood.

Example 13 Preparation of a Triamcinolone Acetonide ContainingHA-VS/PEG-(SH)₂ Gel Slurry with Hyaluronic Acid

2 g hyaluronic acid [9.4×10⁴ cps (3% in water)] was weighed into a 250mL round bottom flask. 100 mL sterile saline was added to the hyaluronicacid in the flask. The flask was attached to a Rotavap (Buchi) androtated at 50 rpm for at least 16 hrs to form a 2% hyaluronic acidsolution. Using the HA-VS/PEG-(SH)₂ gel slurry containing triamcinoloneacetonide (as prepared in Example 10 or 11), a series of formulationswere prepared in which the a triamcinolone acetonide containingHA-VS/PEG-(SH)₂ gel slurry was mixed with hyaluronic acid. The volumesof hyaluronic acid solution and the triamcinolone acetonide-containingHA-VS/PEG-(SH)₂ gel slurry used to prepare these formulations are shownin the table below:

TABLE 3 VOLUME TRIAMCINOLONE VOLUME ACETONIDE CONTAINING HYALURONICHA-VS/PEG-(SH)2 GEL FORMULATION ACID (ML) SLURRY (ML) 1 1 5 (singleextrusion slurry) 2 2 4 (single extrusion slurry) 3 3 3 (singleextrusion slurry) 4 4 2 (single extrusion slurry) 5 5 1 (singleextrusion slurry) 6 1 5 (double extrusion slurry) 7 2 4 (doubleextrusion slurry) 8 3 3 (double extrusion slurry) 9 4 2 (doubleextrusion slurry) 10 5 1 (double extrusion slurry)

The indicated volumes of hyaluronic acid solution and the triamcinoloneacetonide-containing HA-VS/PEG-(SH)2 gel slurry, as identified in thetable above, were added to a 15 mL sterile centrifuge tube. The cap wasplaced on the tube and the tube was inverted back and forth until thecomponents were well mixed. Each formulation was then transferred into a10 mL glass syringe that had a syringe cap after which the plunger wasinserted and the excess air was expelled. The syringe cap was thentightened. The above steps were performed in a biohood.

Example 14 Preparation of Samples for Release Study of TriamcinoloneAcetonide

1.5 mL of the triamcinolone acetonide-containing HA-VS/PEG-(SH)₂ gel(prepared according to Example 11) was transferred to a 20 mL glassscintillation vial. 15 mL PBS (pH 7.4) was pipetted into thescintillation vial containing the gelled material. The scintillationvial was closed with a screw lid and the vial was placed on a rockingshaker (Barnstead International, Model M26125) in a 37° C. oven.

Example 15 Sampling of Release Study Buffer

At various time points, the scintillation vial that contained thetriamcinolone acetonide-loaded gel and PBS buffer (as described inExample 14) was removed from the 37° C. oven. The residual gel slurrywas allowed to settle to the bottom of the scintillation vial. The screwlid was removed and 13 mL of the PBS buffer was removed using aserological pipette and transferred into a 50 mL plastic centrifugetube. 13 ml fresh PBS (pH 7.4) was then pipetted into the gel-containingscintillation vial.

Example 16 HPLC Analysis of the Triamcinolone Acetonide ContainingRelease Media

The 13 mL buffer sample (Example 15) was diluted to 40 mL with 80:20MeOH:H2O. The sample was vortexed and approx 1 mL was transferred to aHPLC vial. The triamcinolone acetonide content of the buffer sample wasdetermined using the following chromatographic conditions:

HPLC: Agilent 1100 series

Column: Zorbax SB-C18, 5μ, 4.6×160 mm

Column Temperature: 30° C.

Flow rate: 1.0 mL/min

Detection: UV at 239 nm

Run Time: 8 minutes

Injection Volume: 50 μl

Mobile phase: 0.05% TFA in ACN: 0.05% TFA in H2O, 56:44

Retention Time of TA: ˜3.3 min

The amount of triamcinolone acetonide in the buffer samples wasquantified by correlating the peak area to a triamcinolone acetonideconcentration through a calibration curve. The samples for thetriamcinolone acetonide calibration curves were prepared by taking astock solution of triamcinolone acetonide in methanol and then seriallydiluting the stock solution with 0.05% TFA in ACN: 0.05% TFA in H₂O,56:44. These samples were analyzed using the chromatographic conditionsabove and the peak area obtained was plotted against the triamcinoloneacetonide concentration. The percent release is illustrated in FIG. 2;the cumulative mass released is shown in FIG. 3; and the amount releaseper sampling point is shown in FIG. 4.

Samples were drawn every 24 hours Monday-Friday; sampling was notconducted on Saturday/Sunday.

TABLE 4 Sampling Sampling No. Times (days) 1 1 2 2 3 3 4 7 5 8 6 9 7 108 11 9 14 10 15

As shown in FIG. 2, essentially all drug was released by sampling point12. Drug was released in a linear fashion over time, and in a controlledmanner. Advantageously, essentially all drug was released rather thanhaving a significant amount of drug remaining entrapped within the gel.Moreover, rather than releasing drug in an initial burst fashion, drugwas released in a slow and sustained manner over time. FIG. 3 similarlyillustrates cumulative release of drug, in milligrams, over samplingpoints. As illustrated in FIG. 4, the amount of drug released from thegel was essentially constant between sampling points, indicating alinear release of drug in a controlled and sustained manner over time.

Example 17 Intra-Articular Injection of an Exemplary HA-VS/PEG-(SH)₂ GelSlurry

A sample of the HA-VS/PEG-(SH)₂ gel slurry (prepared as in Example 5)was injected intra-articularly into the stifle (knee) of skeletallymature female goats along with additional test materials 2-4 to providepoints of reference. See also D. Jackson and T. Simon, Osteoarthritisand Cartilage, Vol. 14, Issue 12, p. 1248-125, for additionaldescription related to the goat model used.

-   -   TEST MATERIAL 1: HA-VS/PEG-(SH)₂ gel (Example 5)    -   TEST MATERIAL 2: PEG diacrylate crosslinked with a bisthiol        crosslinker    -   TEST MATERIAL 3: 4-arm lysine functionalized PEG that has been        crosslinked to form a gel    -   TEST MATERIAL 4: gel made from PEG diacrylate (material was        autoclaved)

See Examples 31-33 for preparations of Test Materials 2-4. Allinjections were performed under strict asepsis. The animals wereanesthetized with an intravenous injection of diazepam (0.1-0.5 mg/kg)and ketamine (4.4-7.5 mg/kg) to effect. Each knee was physicallyexamined for drawer, range of motion, swelling, temperature, crepitus,patella tracking, and valgus/varus abnormalities.

All injections were conducted utilizing routine aseptic techniques. Theleft and right stifles were prepared for injection by clipping theareas, then cleansing them with chlorohexidine scrub. The animal wasplaced in dorsal recumbency. The right stifle was cleansed withchlorohexidine scrub alternating with 70% isopropyl alcohol three timesand painted with iodine solution.

A standard technique was used to inject each stifle joint. A 2-inch by21 gauge sized sterile needle was introduced into the intra-articularspace via an anteromedial approach. The lateral intercondylar notch wallof the medial femoral condyle was felt and the needle backed slightlyoff. 1.5 ml of the HA-VS/PEG(SH)₂ gel slurry was injected into the rightjoint. The injection needle was removed and pressure was maintained onthe injection site. The injected stifle joint was then cycled 20-timesthrough a full range of motion.

Post-injection checks were made for any animal displaying signs ofdistress and discomfort, and additional analgesics were given if needed.All treatments were recorded in the appropriate study documentation.

The injected animals were humanely sacrificed at 24±1 hours post initialinjection with an intravenous injection consisting of diazepam 0.22mg/kg and ketamine 10 mg/kg for induction of general anesthesia.Following this, the anesthetized animals were given an IV overdose ofconcentrated potassium chloride (KCl) until the cardiac arrest had beenverified.

After collection of the knee joints, the joints were opened and grossevaluation as described in Table 5 of the injected stifle joints wasperformed. No photodocumentation was made.

TABLE 5 Gross Evaluation and Sample Collection Gross Sample SampleEvaluation collection Score Synovial Fluid (left and right) X X X Leftand Right Knee joints X X Left and Right synovium X X

Additionally, semi-quantitative grading of the joint by a singleobserver as outlined in Table 6 was performed.

TABLE 6 Gross Joint Evaluation Grading Scale Score Coloration HyperemiaEdema 0 Normal None None 1 Slightly yellow Slight Slight 2 YellowModerate Moderate 3 Marked Marked

The total joint gross evaluation score was the sum of the coloration,hyperemia, and edema scores (0-8 points). See FIG. 6.

After collection of the synovial fluid from the opened joints, the totalvolume was recorded. The fluid was grossly evaluated for viscosity,clarity and color and semi-quantitatively graded as per Table 7. With ahemocytometer, total white cell counts were done. Additionally, asynovial fluid smear was made for differential microscopic analysis.Remaining synovial fluid was preserved frozen in individually labeledcryovials at −80° C. A synovial fluid smear was retained for potentialfuture analysis.

TABLE 7 Description and Score for Synovial Fluid Score Color ClarityString 0 S = STRAW C = CLEAR N = NORMAL 1 P = PINK H = HAZY A = ABNORMAL2 Y = YELLOW/R = RED D = CLOUDY W = WATERY 3 B = BLOODY T = TURBID

Total synovial fluid score was the sum of the color, clarity and stringscores (0-8 points).

Results are provided in graphical fashion in FIGS. 5-8. As can be seenin FIG. 5, an exemplary gel having the features described hereindemonstrated a synovial fluid leukocyte count that was significantlylower than those observed for Test Materials 2-4. Indeed, the leukocytecounts for Test Materials 2-4 were approximately 5 times, 9 times and 8times greater than observed for Test Material 1. While Test Materials2-4 exhibit in-vitro behavior (e.g., chemistry, gel properties, ease ofadministration, etc.) indicating their suitability for pharmaceuticaluse, these results illustrate the clear superiority of Test Material 1and materials similar thereto, in terms of having significantly lowpro-inflammatory properties when examined in a goat model in comparisonto seemingly comparable test materials. Surprisingly, all otherindicators pointed to the suitability of the other test materials forviscosupplementation and other related uses.

FIG. 6, demonstrating absolute synovial fluid leukocyte count(absolute=total volume×synovial fluid leukocyte count) for the injectedgoat knees further supports the above. That is, exemplary Test Material1, demonstrates a strikingly lower inflammatory response in the goatmodel than do Test Materials 2-4, based upon absolute synovial fluidleukocyte count. Values for Test Materials 2-4 are approximately 4-fold,12-fold, and over 9-fold greater than for Test Material 1—indicating thesurprising and notable superiority of Test Material 1 when evaluated inthe goat knee.

FIG. 7 is a graphical representation of the synovial fluid leukocytedifferential distribution (means for groups) for the injected goat kneesrelative to test material treatment group evaluated at 24 hrs after 1.5ml injection as described in Example 17. Shown for each Test Material isthe distribution of polymorphonuclear leukocytes (PMN), lymphocytes,monocytes, and eosinophils (Eos). PMNs and Eos are important cellularparticipants in a variety of acute and chronic inflammation. Thepercentage of PMNs for Test Material 1 (relative to lympocytes,monocytes and eosinophils) was significantly lower than for other testmaterials (approx 50% relative to 70% and greater for test materials2-4)—a yet additional indication of the advantageously lowpro-inflammatory properties of exemplary Test Material 1 in comparisonto the other materials examined.

Finally, FIG. 8 illustrates the average total scores for synovial fluid,joint tissues, and combined synovial fluid and joint tissues scores(Table 6) for the injected goat knees for each representative TestMaterial.Total Gross Score=Synovial Fluid Score+Total Joint Score.

Maximum score for Synovial Fluid or Total Joint Score is 8 with 0 beingnormal;

Maximum score for Total Gross Score is 16 with 0 being normal.

As illustrated in FIG. 8, a striking result is shown for TestMaterial 1. Indeed for all scores, determined by visual inspection asdescribed above, Test Material 1 is shown to illicit essentially noinflammatory response, with scores for synovial fluid, joint tissues,and the combination considered to be normal or nearly normal. Incontrast, representative Test Materials 2-4 resulted in visualcharacteristics in both the synovial fluid and joint that werenon-normal, and indicated inflammation in the knee joint resulting fromadministration of the test material. These results demonstrate thesurprising and beneficial properties of illustrative Test Material 1, interms of suitability for therapeutic applications in-vivo.

Example 18 Synthesis of HA-VS/PEG-(SH)₄ Gel

A solution of the HA-VS, as prepared in Example 1, is diluted usingdeionized water to a concentration of 12.6 mg/mL. 18 mL HA-VS solutionis placed into a 20 mL sterile syringe. The HA-VS solution is filteredthrough a 0.2 um sterile syringe filter into a sterile 50 mL centrifugetube. 200 mg PEG(SH)₄, C(CH₂O(CH₂CH₂O)_(n)CH₂CH₂SH)₄, [Laysan Bio Inc,Mw 10,000, Item# 4 armPEG-SH-10 kD-1 g] (e-beamed) is added to sterilefiltered 2 mL 0.17M sodium phosphate in 1M saline (pH7.4). Oncedissolved, the PEG-(SH)₄ solution is added to the HA-VS solution. Theresultant solution is mixed thoroughly. The HA-VS/PEG-(SH)₄ solution isthen allowed to gel at room temperature. The gelled material can beconverted into a gel slurry in a similar manner to that described inExamples 3 and 4. The gel can be prepared in the presence oftriamcinolone acetonide using a similar procedure to that described inExamples 9, 10 and 11. Hyaluronic acid can be added to the gelformulation in a similar procedure as that described in Example 8.Hyaluronic acid can be added to the triamcinolone acetonide gelformulation in a similar procedure as that described in Example 13.

Example 19 Synthesis of Carboxymethyl-Hyaluronic Acid (CM-HA ORCarbylan™)

Aqueous NaOH solution (200 ml, 45% w/v) was added to a 500 mL beaker andwas stirred (magnetic stirrer) at ambient temperature. Hyaluronic acidpowder (20 g) [Novozymes, MW 0.8-1.0 million] was added to a 500-mlbeaker. After standing for 2 hours, the hyaluronic acid mixture wastransferred into a 4 L beaker with 1,500 ml isopropanol and aTeflon-coated magnetic stir bar, and then a solution of 20 g ofchloroacetic acid in 500 ml isopropanol was added with magneticstirring. After stirring for 1 hour at ambient temperature, the stirringwas stopped and the material was allowed to settle for approx. 10-20minutes. As much of the supernatant as possible was aspirated from themixture. 1,000 ml of distilled water was added to the resultant mixture.Once dissolved, the solution pH was adjusted to ca. pH 7.0 by adding 6.0N HC1. The solution is then made up to 2 L using DI water. The solutionwas purified by tangential flow filtration (TFF) using 10 L DI water asthe exchange buffer.

Additionally, the structure, synthesis and characterization ofcarboxymethyl hyaluronic acid is described in International PatentPublication No. 2005/056608 (FIG. 5 and Example 3), related portionsthereof are incorporated herein by reference in their entirety.

Example 20 Synthesis of Carboxymethyl-Hyaluronic Acid-Dithiobis(Propanoic Dihydrazide (CM-HA-DTPH OR Carbylan™-S)

3,3′-Dithiobis (propanoic dihydrazide) (DTP) was synthesized aspreviously described. (Vercruysse, K. P.; Marecak, D. M.; Marecek, J.F.; Prestwich, G. D. “Synthesis and in vitro degradation of newpolyvalent hydrazide cross-linked hydrogels of hyaluronic acid.”Bioconjugate Chem. (1997) 8: 686-694; Shu, X. Z.; Liu, Y.; Luo, Y.;Roberts, M. C.; Prestwich, G. D. “Disulfide crosslinked hyaluronanhydrogels.” Biomacromolecules (2002) 3: 1304-1311). DTP (16.7 g, 0.07mol) was added to the Carbylan™ solution prepared above, and thesolution pH was adjusted to 4.75 by adding either HCl or NaOH solution.Then, 0.384 g 1-ethyl-3[3-(dimethylamino) propyl] carbodiimide (EDC)[Sigma-Aldrich] was added, and the solution pH was maintained at a pH of4.75 by adding 6.0 N HCl with continuous magnetic stirring at roomtemperature.

After 4 h, 50 g of dithiothreitol (DTT) [Biovectra] was added, and thesolution pH was adjusted to 8.5 by adding conc. NaOH solution. Thenafter 12-24 h under magnetic stirring at room temperature, the pH of thereaction mixture was adjusted to pH 3.0 by the addition of 6.0 N HCl.The acidified solution was purified and concentrated using tangentialfluid filtration (TFF) using 20 L 1 mM HC1, pH 3.0. The solution wasthen concentrated to approx 1 L.

The structure, synthesis, and characterization ofcarboxymethyl-hyaluronic acid-dithiobis(propanoic dihydrazide isdescribed in International Patent Publication No. 2005/056608 (FIG. 5and Example 4), related portions of which are incorporated herein byreference in their entirety.

Example 21 Synthesis of a CM-HA-DTPH/PEG-(Acrylate)₂ Gel

A solution of the CM-HA-DTPH, as prepared in Example 20, is dilutedusing deionized water to a concentration of 17.5 mg/mL. 30 mL CM-HA-DTPHsolution is placed into a 60 mL sterile syringe. The CM-HA-DTPH solutionis filtered through a 0.2 um sterile syringe filter into a sterile 50 mLcentrifuge tube. A 40 mg/mL solution of PEG-(acrylate)2 [Laysan Bio Inc,MW 3400, Item# ACRL-PEG-ACRL3400-1 g] is prepared by dissolving 600 mgPEG-(acrylate)₂ in 15 mL 0.2M sodium phosphate buffer (pH 7.4). ThePEG-(acrylate)₂ solution is transferred to a 20 mL sterile syringe andis filtered through a 0.2 um sterile syringe filter. 20 mL of thesterile filtered CM-HADTPH is transferred to a sterile 50 mL centrifugetube. 10 mL of the PEG-(acrylate)2 solution is added to the CM-HADTPHsolution. The resultant solution is mixed thoroughly. TheCM-HA-DTPH/PEG-(acrylate)₂ solution is then allowed to gel at roomtemperature.

Example 22 CM-HA-DTPH/PEG-(Acrylate)₂ Gel Slurry

The CM-HA-DTPH/PEG-(acrylate)₂ gel (as prepared in Example 21) isconverted to a gel slurry using a procedure similar to that described inExamples 3 and 4 respectively.

Example 23 Triamcinolone Acetonide-Containing CM-HA-DTPH/PEG-(Acrylate)₂Gel

A solution of the CM-HA-DTPH, as prepared in Example 20, is dilutedusing deionized water to a concentration of 14 mg/mL. 11 mL CM-HA-DTPHsolution is placed into a 20 mL sterile syringe. The CM-HA-DTPH solutionis filtered through a 0.2 um sterile syringe filter into a sterile 50 mLcentrifuge tube. A 50 mg/mL solution of PEG-(acrylate)₂ [Laysan Bio Inc,MW 3400, Item# ACRL-PEG-ACRL-3400-1 g] is prepared by dissolving 40.1 mgPEG-(acrylate)₂ in 0.802 mL deionized water. The PEG-(acrylate)₂solution is transferred to a 1 mL sterile syringe and is filteredthrough a 0.2 um sterile syringe filter. 10 mL of the sterile filteredCM-HA-DTPH is transferred to a sterile 50 mL centrifuge tube. 20 mg oftriamcinolone acetonide (Spectrum Chemicals, U.S.P grade, micronized)was added to the CM-HA-DTPH solution. The cap of the centrifuge tube wasplaced on the tube and the solution was inverted back and forth untilthe triamcinolone acetonide was homogeneously mixed with the CM-HA-DTPH.250 μL of a 0.5 M sodium phosphate solution is added to the CM-HA-DTPHsolution. The resultant solution is mixed thoroughly. 380 μL [19 mgPEG-(acrylate)₂] of the sterile 50 mg/mL PEG-(acrylate)₂ solution isadded to the CM-HA-DTPH solution. The resultant solution is mixedthoroughly. The CM-HA-DTPH/PEG-(acrylate)₂ solution that containedtriamcinolone acetonide is then placed in a 37° C. incubator for atleast 16 hours. At this stage the CM-HA-DTPH/PEG-(acrylate)₂ solutionthat contained triamcinolone acetonide is crosslinked to form a gel. Thegelled material is then removed from the incubator.

The synthesis of the gel is repeated using 33 mg, 50 mg, 75 mg, 100 mg,125 mg, 150 mg, 175 mg, 200 mg, 225 mg, 250 mg, 375 mg, 400 mg and 500mg triamcinolone acetonide respectively.

The gels were converted into a gel slurry using a similar procedure tothat described in Example 3 and 4.

Example 24 Synthesis of Triamcinolone Acetonide-ContainingHA-VS-PEG-(SH)₂ Gel Slurry

Triamcinolone acetonide-containing HA-VS-PEG-(SH)₂ gels are preparedusing a procedure similar to that described in Example 9 with theexception that 33 mg, 50 mg, 75 mg, 100 mg, 125 mg, 150 mg, 175 mg, 200mg, 225 mg, 250 mg, 375 mg, 400 mg and 500 mg triamcinolone acetonide,respectively, were used to prepare each gel.

The gels were converted into a gel slurry using a similar procedure tothat described in Example 3 and 4.

Example 25 Synthesis of a CM-HA-DTPH/PEG-(Acrylate)₄ Gel

A solution of the CM-HA-DTPH, as prepared in Example 20, is dilutedusing deionized water to a concentration of 14 mg/mL. 11 mL CM-HA-DTPHsolution is placed into a 20 mL sterile syringe. The CM-HA-DTPH solutionis filtered through a 0.2 um sterile syringe filter into a sterile 50 mLcentrifuge tube. A 50 mg/mL solution of PEG-(acrylate)₄ [Laysan Bio Inc,Mw 10,000, Item# 4arm-PEG-ACRL10K-1 g] is prepared by dissolving 40.1 mgPEG-(acrylate)₄ in 0.802 mL deionized water. The PEG-(acrylate)₄solution is transferred to a 1 mL sterile syringe and was filteredthrough a 0.2 um sterile syringe filter. 10 mL of the sterile filteredCM-HADTPH is transferred to a sterile 50 mL centrifuge tube. 250 μL of a0.5 M sodium phosphate solution is added to the CM-HA-DTPH solution. Theresultant solution is mixed thoroughly. 560 μL [28 mg PEG-(acrylate)₄]of the sterile 50 mg/mL PEG-(acrylate)₄ solution is added to theCM-HA-DTPH solution. The resultant solution is mixed thoroughly. TheCM-HA-DTPH/PEG-(acrylate)₄ solution is then placed in a 37° C. incubatorfor at least 16 hours. At this stage the CM-HA-DTPH/PEG-(acrylate)₄solution is crosslinked to form a gel. The gelled material is thenremoved from the incubator. The gelled material can be converted into agel slurry in a similar manner as to that described in Example 3 and 4.The gel can be prepared in the presence of triamcinolone acetonide usinga similar procedure to that described in Examples 9, 10 and 11.Hyaluronic acid can be added to the gel formulation in a similarprocedure as that described in Example 8. Hyaluronic acid can be addedto the triamcinolone acetonide gel formulation in a similar procedure asthat described in Example 13.

Example 26 Synthesis of Hyaluronic Acid-Dithiobis (Propanoic Dihydrazide(HA-DTPH)

3,3′-Dithiobis (propanoic dihydrazide) (DTP) was synthesized asdescribed previously. (Vercruysse, K. P.; Marecak, D. M.; Marecek, J.F.; Prestwich, G. D. “Synthesis and in vitro degradation of newpolyvalent hydrazide cross-linked hydrogels of hyaluronicacid.”Bioconjugate Chem. (1997) 8: 686-694; Shu, X. Z.; Liu, Y.; Luo,Y.; Roberts, M. C.; Prestwich, G. D. “Disulfide crosslinked hyaluronanhydrogels.”Biomacromolecules (2002) 3: 1304-1311). DTP (16.7 g, 0.07mol) was added to a hyaluronic acid (20 g hyaluronic acid [Mw 0.8-1.0million] dissolved in 1000 mL DI water) solution prepared above, and thesolution pH was adjusted to 4.75 by adding either HCl or NaOH solution.Then, 0.384 g 1-Ethyl-3-[3-(dimethylamino) propyl] carbodiimide (EDC)[Sigma-Aldrich] was added, and the solution pH was maintained at a pH of4.75 by adding 6.0 N HCl with continuous magnetic stirring at roomtemperature. After 4 h, 50 g of dithiothreitol (DTT) [Biovectra] wasadded, and the solution pH was adjusted to 8.5 by adding conc. NaOHsolution. Then after 12-24 h under magnetic stirring at roomtemperature, the pH of the reaction mixture was adjusted to pH 3.0 bythe addition of 6.0 N HCl. The acidified solution was purified andconcentrated using tangential fluid filtration (TFF) using 20 L 1 mMHC1, pH 3.0. The solution was then concentrated to approx 1 L.

Example 27 Synthesis of a HA-DTPH/PEG-(Acrylate)₂ Gel

A solution of the HA-DTPH, as prepared in Example 26, is diluted usingdeionized water to a concentration of 14 mg/mL. 11 mL HA-DTPH solutionis placed into a 20 mL sterile syringe. The HA-DTPH solution is filteredthrough a 0.2 um sterile syringe filter into a sterile 50 mL centrifugetube. A 50 mg/mL solution of PEG-(acrylate)₂ [Laysan Bio Inc, MW 3400,Item# ACRL-PEG-ACRL-3400-1 g] is prepared by dissolving 40.1 mgPEG-(acrylate)₂ in 0.802 mL deionized water. The PEG-(acrylate)₂solution is transferred to a 1 mL sterile syringe and is filteredthrough a 0.2 um sterile syringe filter. 10 mL of the sterile filteredHA-DTPH is transferred to a sterile 50 mL centrifuge tube. 250 μL of a0.5 M sodium phosphate solution is added to the HA-DTPH solution. Theresultant solution is mixed thoroughly. 380 μL [19 mg PEG-(acrylate)₂]of the sterile 50 mg/mL PEG-(acrylate)₂ solution is added to the HA-DTPHsolution. The resultant solution is mixed thoroughly. TheHA-DTPH/PEG-(acrylate)₂ solution is then placed in a 37° C. incubatorfor at least 16 hours. At this stage the HA-DTPH/PEG-(acrylate)₂solution is crosslinked to form a gel. The gelled material is thenremoved from the incubator.

Example 28 HA-DTPH/PEG-(Acrylate)₂ Gel Slurry

The HA-DTPH/PEG-(acrylate)₂ gel (as prepared in Example 27) is convertedto a gel slurry using a procedure similar to that described in Examples3 and 4, respectively.

Example 29 Triamcinolone Acetonide Containing HA-DTPH/PEG-(Acrylate)₂Gel

A solution of the CM-HA-DTPH, as prepared in Example 20, is dilutedusing deionized water to a concentration of 17.5 mg/mL. 30 mL CM-HA-DTPHsolution is placed into a 60 mL sterile syringe. The CM-HA-DTPH solutionis filtered through a 0.2 um sterile syringe filter into a sterile 50 mLcentrifuge tube. 100 mg sterile triamcinolone acetonide powder is addedand the resultant mixture is mixed thoroughly. A 40 mg/mL solution ofPEG-(acrylate)₂ [Laysan Bio Inc, MW 3400, Item# ACRL-PEG-ACRL3400-1 g]is prepared by dissolving 600 mg PEG-(acrylate)₂ in 15 mL 0.2M sodiumphosphate buffer (pH 7.4). The PEG-(acrylate)₂ solution is transferredto a 20 mL sterile syringe and is filtered through a 0.2 um sterilesyringe filter. 20 mL of the sterile filtered CM-HADTPH is transferredto a sterile 50 mL centrifuge tube. 10 mL of the PEG-(acrylate)₂solution is added to the CM-HA-DTPH solution. The resultant solution ismixed thoroughly. The CM-HA-DTPH/PEG-(acrylate)₂ solution is thenallowed to gel at room temperature.

The synthesis of the gel is repeated using 33 mg, 50 mg, 75 mg, 125 mg,150 mg, 175 mg, 200 mg, 225 mg, 250 mg, 375 mg, 400 mg and 500 mgtriamcinolone acetonide, respectively.

The gels are converted into a gel slurry using a similar procedure tothat described in Example 3 and 4.

Example 30 Synthesis of a HA-DTPH/PEG-(Acrylate)₄ Gel

A solution of the HA-DTPH, as prepared in Example 20, is diluted usingdeionized water to a concentration of 14 mg/mL. 11 mL HA-DTPH solutionis placed into a 20 mL sterile syringe. The HA-DTPH solution is filteredthrough a 0.2 um sterile syringe filter into a sterile 50 mL centrifugetube. A 50 mg/mL solution of PEG-(acrylate)₄ [Laysan Bio Inc, Mw 10,000,Item# 4arm-PEG-ACRL-10K-1 g] is prepared by dissolving 40.1 mgPEG-(acrylate)₄ in 0.802 mL deionized water. The PEG-(acrylate)₄solution is transferred to a 1 mL sterile syringe and was filteredthrough a 0.2 um sterile syringe filter. 10 mL of the sterile filteredHA-DTPH is transferred to a sterile 50 mL centrifuge tube. 250 μL of a0.5 M sodium phosphate solution is added to the HA-DTPH solution. Theresultant solution is mixed thoroughly. 560 μL [28 mg PEG-(acrylate)₄]of the sterile 50 mg/mL PEG-(acrylate)₄ solution is added to the HA-DTPHsolution. The resultant solution is mixed thoroughly. TheHA-DTPH/PEG-(acrylate)₄ solution is then placed in a 37° C. incubatorfor at least 16 hours. At this stage the HA-DTPH/PEG-(acrylate)₄solution is crosslinked to form a gel. The gelled material is thenremoved from the incubator. The gelled material can be converted into agel slurry in a similar manner as to that described in Example 3 and 4.The gel can be prepared in the presence of triamcinolone acetonide usinga similar procedure as to that described in Example 9, 10 and 11.Hyaluronic acid can be added to the gel formulation in a similarprocedure as that described in Example 8. Hyaluronic acid can be addedto the triamcinolone acetonide gel formulation in a similar procedure asthat described in Example 13.

Example 31 Preparation of Peg-Diacrylate Gel (Test Material 4)

1.466 g of Poly(ethylene glycol)-diacrylate [PEG-DA] (Laysan Bio, Item#ACRL-PEG-ACRL-3400-1 g) was weighed into a sterile 125 mL bottle. 22 mLof sterile saline was added to the PEG-DA. Once dissolved, thePEG-DA/NaCl was filtered through a 0.2 um syringe filter into sanitizedErlenmeyer flask. A 0.150M Carbonate Buffer, pH 8.2 was filtered througha 0.2 um syringe filter and 1 mL of this sterile solution was added toPEG-DA solution. The flask was capped with a rubber septum and thesolution was degassed by bubbling with nitrogen for 10 minutes. A 0.2 umfilter is attached to the gas line to ensure the air is sterile. A 400mg/mL sodium ascorbate solution was prepared by adding 1.2 g sodiumascorbate into a sintered glass vial with a septum lid. 3 mL DI waterwas added to the vial. Once dissolved, the solution was filtered through0.2 um syringe filter into a 15 ml sterile centrifuge tube. 0.8 mL ofsterile filtered 400 mg/mL sodium ascorbate was added to the PEG-DAsolution. 0.8 of a sterile filtered 400 mg/mL sodium persulfate solutionwas added to the PEG-DA solution. The solution was mixed by swirling thesolution. The flask was capped with red rubber septa and the solutionwas degassed by bubbling with nitrogen for 15 minutes. A 0.2 um filterwas attached to the gas line to ensure the nitrogen used to degas thesolution. The solution was placed in a 37° C. for at least 18 hrs toform a gel. The gel was transferred to a 30 mL syringe. A 23 mm circulardisk of the mesh was cut from a sheet of mesh using a 23 mm leatherpunch. The mesh disk was placed into a 25 mm polycarbonate syringefilter that has the support screens removed. The gel was extrudedthrough a mesh (1 mm×1 mm openings) into a 250 mL beaker. 100 mL sterilesaline was added to 25 mL of the extruded gel. After 40 min, the salinesupernatant was poured off and an additional 125 mL sterile saline wasadded. This was repeated 3 times. After the final wash, 45 ml of theswollen gel was added to 45 mL saline and the slurry was gently mixed.The pH of the resultant solution was adjusted to between 7.0 and 7.4using a combination of 1N NaOH and 1 N HCl. 1.5 mL of the this gelslurry was filled into a 5 mL glass syringe. A syringe cap was used toclose the syringe. The syringe was then autoclaved at 250° C. for 15min.

Example 32 Preparation of Peg-Diacrylate/Bisthiol Gel (Test Material 2)

630 mg Poly(ethylene glycol)-diacrylate [PEG-DA] (Laysan Bio, Item#ACRL-PEG-ACRL-3400-1 g) was weighed into a 20 mL glass scintillationvial. 6 mL DI water was added. Once dissolved, the solution was filteredthrough a 0.2 um syringe filter. 48 mg N,N′-Bis(acryloyl)cystamine(Sigma, A4929) was dissolved in 6 mL tetrahydrofuran (THF) in a glassscintillation vial. Once dissolved this solution was mixed with thePEG-DA solution. A septum screw cap was placed on the vial and thesolution was degassed by bubbling with nitrogen for 10 minutes. 50 uL ofa 400 mg/mL solution of sodium ascorbate (prepared using DI water andfiltered through a 0.2 um syringe filter) was added to the PEG-DAsolution. 50 uL of a 400 mg/mL solution of sodium persulfate (preparedusing DI water and filtered through a 0.2 um syringe filter) was addedto the PEG-DA solution. The septum lid was replaced and the solution wasdegassed by bubbling with nitrogen for 10 minutes. The solution wasplaced in an oven that was set at 60° C. The solution had turned into agel after 15 minutes. The gel was removed from the oven and was allowedto cool to room temperature. The gel was transferred to a 30 mL syringe.A 23 mm circular disk of the mesh was cut from a sheet of mesh using a23 mm leather punch. The mesh disk was placed into a 25 mm polycarbonatesyringe filter that has the support screens removed. The gel wasextruded through a mesh (˜0.8 mm×˜0.8 mm openings) into a 400 mL beaker.200 mL DI water was added to the extruded gel. After 45 min, thesupernatant was poured off and an additional 200 mL DI water was added.This was repeated 4 times. The wash steps were then repeated 3 timesusing 0.9% saline. The supernatant liquid was removed and the remaininggel was extruded through the mesh again (as described above). 1.5 mL ofthe gel slurry was filled into a 5 mL glass syringe. A syringe cap wasused to close the syringe. The syringe was then autoclaved at 250° C.for 15 min.

Example 33 Preparation of Peg-(Lys)₄ Gel (Test Material 3)

1.0 g of a PEG-(lys)4 [a 4-arm polyethylene glycol (Mw 10,000) that hasits terminal hydroxyl groups functionalized with gutarice anhydride andthen with lysine] was weighed into a 60 mL glass bottle. 34 mLdichloromethane was added to the PEG-(lys)4. 333 uL ofdiisopropylcarbodiimide (Fluka, 38370) was added to the solution. Thesolution had changed to a gel after about 30 minutes. The gelation wasallowed to continue for at least 18 hrs. The gel was transferred to a 30mL syringe. A 23 mm circular disk of the mesh was cut from a sheet ofmesh using a 23 mm leather punch. The mesh disk was placed into a 25 mmpolycarbonate syringe filter that has the support screens removed. Thegel was extruded through a mesh (˜0.38 mm×˜0.38 mm openings) into a 400mL beaker. 33 mL of the gel was washed 330 mL acetone. After 30 min, theacetone was removed. The wash process was repeated 4 times. The gel wasthen dried under vacuum (Approx. 18 hr under vacuum). 771 mg of thedried gel was added to 52 mL saline and the gel was allowed to swell for5 hrs. The gel was then meshed through a mesh (˜0.38 mm×˜0.38 mmopenings). 1.5 mL of the this gel slurry was filled into a 5 mL glasssyringe. A syringe cap was used to close the syringe. The syringe wasthen autoclaved at 250° C. for 15 min.

Example 34 In-Vivo Study: Intra-Articular Injection of a CrosslinkedHA-VS-PEG-(SH)₂ Hydrogel Containing a Corticosteroid

A lightly crosslinked hydrogel prepared by reaction ofvinyl-sulfone-modified hyaluronic acid with PEG-dithiol(HA-VS-PEG-(SH)₂), containing the corticosteroid, triamcinoloneacetonide, was injected into the intraarticular space of the stiflejoint of female goats. Morphological, synovial fluid and histologicalexaminations were conducted to evaluate local and systemic effects ofsuch injections. Details of the study are provided below.

A. Test Materials

Test Material 1.

HA-VS-PEG-(SH)₂ (cross-linked HA-based hydrogel absent drug) wasprepared as follows.

A solution of the HA-VS, prepared as in Example 1, was diluted usingdeionized water to a concentration of 14 mg1 mL. 11 mL HA-VS solutionwas placed into a 20 mL sterile syringe. The HA-VS solution was filteredthrough a 0.2 um sterile syringe filter into a sterile 20 mL syringe. A50 mg/mL solution of PEG(SH)₂ was prepared by dissolving 40.1 mgPEG-(SH)2 in 0.802 mL deionized water. The PEG-(SH)₂ solution wastransferred to a 3 mL sterile syringe and was filtered through a 0.2 μmsterile syringe filter. 10 mL of the sterile filtered HA-VS wastransferred to a sterile 50 mL centrifuge tube. 250 uL of a 0.5 M sodiumphosphate solution was added to the HA-VS solution. The resultantsolution was mixed thoroughly. 380 mL of the sterile 50 mg/mL PEG-(SH)₂solution was added to the HA-VS solution. The resultant solution wasmixed thoroughly. The HA-VS/PEG-(SH)₂ solution was then placed in a 37°C. incubator for at least 16 hours. At this stage the HA-VS/PEG-(SH)₂solution had crosslinked to form a gel. The gelled material was thenremoved from the incubator.

Test Material 2.

HA-VS-PEG-(SH)₂-triamcinolone acetonide (“HA-VS-PEG(SH)₂-TA”) wasprepared as follows.

100.2 mg of triamcinolone acetonide (Sicor, U.S.P grade, micronized) wasmixed in 2 mL deionized water in a 20 mL scintillation vial. Aftersonicating for 20 minutes, the material was autoclaved at 250° F. for 15minutes. 9 mL of the HA-VS solution, prepared as in Example 1 atconcentration of 18.3 mg/mL was placed into a 20 mL sterile syringe. TheHA-VS solution was filtered through a 0.2 μm sterile syringe filter intoa sterile 10 mL syringe. A 50 mg/mL solution of PEG-(SH)₂ was preparedby dissolving 35 mg PEG-(SH)₂ in 0.7 mL deionized water. The PEG(SH)₂solution was transferred to a 3 mL sterile syringe and was filteredthrough a 0.2 um sterile syringe filter. 7.6 mL of the sterile filteredHA-VS was transferred to the triamcinolone acetonide solution. 370 μldeionized water and 250 uL of a 0.5 M sodium phosphate solution wasadded to the vial containing HA-VS and triamcinolone acetonide. Theresultant solution was mixed thoroughly. 380 μL of the sterile 50 mglmLPEG-(SH)₂ solution was added to the HA-VS/triamcinolone acetonidesolution. The resultant solution was mixed thoroughly. TheHAVS/triamcinolone acetonide/PEG-(SH)₂ solution was then placed in a 37°C. incubator for at least 16 hours. At this stage the HA-VS-PEG-(SH)₂-TAsolution had crosslinked to form a gel. The gelled material was thenremoved from the incubator.

Test Material 3.

Triamcinolone acetonide, 2 mg/ml (Kenalog-10; 10 mg/mL triamcinoloneacetonide diluted with saline to 2 mg/mL)

Test Material 4.

Triamcinolone acetonide, 8 mg/ml (Kenalog-40; 40 mg/mL triamcinoloneacetonide diluted with saline to 8 mg/mL)

Control.

Saline, 0.9% sodium chloride.

All test materials were stored at room temperature prior to use. Foreach Test or Control Material, a 1.5 ml dosage was prepared for eachindividual intra-articular injection.

B. Animals

A total of 24 skeletally mature female goats were used for this study.They were acquired from an approved USDA source. Animals weighed between63 and 97 lbs at the start of the study.

Goats were acquired from an approved USDA source and determined to beCaprine Arthritis Encephalitis (CAE) and Johne's negative prior to beingplaced in this study. Each animal was given a general health evaluation(subject to visual observation for attitude, ease in respiration, andfreedom from diarrhea and nasal discharge) by a qualified veterinarianprior to being placed in the study. The animals were examined for anyevidence of disease or lameness. Acceptability into the study wascontingent on being disease free, clinically sound, and no history ofprior use of the stifle joint. The goats were conditioned for anappropriate period of time as determined by the institution. Animalhousing conditions conformed with applicable laws and regulationsrelating to laboratory animals. The goats were maintained in largeindoor runs (pens) following injection. The goats had unrestrictedactivity at all times.

All animals received approximately 2 lbs. of small ruminant diet per dayas well as loose hay. Tap water was provided ad libitum. Feed waswithheld approximately 12-24 hours prior to anesthesia and water waswithheld approximately 12 hours prior to injections.

Animals were observed daily for general health throughout the course ofthe study. If animals showed any signs of postoperative complications orother signs of disease, pain or stress, appropriate action was taken.Also, in the unlikely event that an animal became injured, ill, ormoribund, care was conducted in accordance with current veterinarymedical practice.

C. Treatment

Study design was as follows.

TABLE 8 Group and Treatment Assignment Sacrifice Time after Right StifleRight Stifle Left Stifle Injection, Group Ear Tag (1.5 ml) (1.5 ml) LeftStifle Injection 1 3171 Test Material 1 Normal Saline 14 days 1 3256Test Material 1 Normal Saline 14 days 1 3831 Test Material 1 NormalSaline 14 days 2 3174 Test Material 2 Normal Saline 14 days 2 3596 TestMaterial 2 Normal Saline 14 days 2 3840 Test Material 2 Normal Saline 14days 3 3133 Test Material 3 Normal Saline 14 days 3 3177 Test Material 3Normal Saline 14 days 3 3833 Test Material 3 Normal Saline 14 days 43589 Test Material 4 Normal Saline 14 days 4 3593 Test Material 4 NormalSaline 14 days 4 3849 Test Material 4 Normal Saline 14 days 5 3267 TestMaterial 1 Normal Saline 28 days 5 3595 Test Material 1 Normal Saline 28days 5 3837* Test Material 1 Normal Saline 28 days (24 days*) 6 3173Test Material 2 Normal Saline 28 days 6 3264 Test Material 2 NormalSaline 28 days 6 3587 Test Material 2 Normal Saline 28 days 7 3591 TestMaterial 3 Normal Saline 28 days 7 3592 Test Material 3 Normal Saline 28days 7 3594 Test Material 3 Normal Saline 28 days 8 3162 Test Material 4Normal Saline 28 days 8 3588* Test Material 4 Normal Saline 28 days (19days*) 8 3590 Test Material 4 Normal Saline 28 days *animal diedprematurely; (total days on study).

Bodyweight, joint circumference and range of motion measurements weretaken from all animals prior to injection (Day 1) and just prior tosacrifice (Day 14 or 28) for each animal.

The basic procedure for injection was identical for all subjects. Allinjections were performed under strict asepsis. The animals wereanesthetized with an intravenous injection of Diazepam (0.1-0.5 mg/kg)and Ketamine (4.4-7.5 mg/kg) to effect. Each knee was physicallyexamined for drawer, range of motion, swelling, temperature, crepitus,patella tracking, and valgus/varus abnormalities

All injections were conducted utilizing routine aseptic techniques. Theleft and right stifles were prepared for injection by clipping theareas, then cleansing them with chlorohexidine scrub. The animal wasplaced in dorsal recumbency. The right stifle was cleansed withchlorohexidine scrub alternating with 70% isopropyl alcohol three timesand painted with iodine solution.

A standard technique was used to inject each stifle joint. A 2-inch by21 gauge sized sterile needle was introduced into the intra-articularspace via an anteromedial approach. The lateral intercondylar notch wallof the medial femoral condyle was felt and the needle backed slightlyoff. 1.5 ml of the appropriate Test Material was injected into the rightjoint. The injection needle was removed and pressure was maintained onthe injection site. The injected stifle joint was then cycled 20-timesthrough a full range of motion. Immediately following this, the leftstifle joint was cleansed with chlorohexidine scrub alternating with 70%isopropyl alcohol three times and painted with iodine solution and 1.5ml of the Control Material was injected into the left stifle joint in asimilar manner as described above for the right stifle. The injectionneedle was removed and pressure maintained on the injection site. Theinjected stifle joint was then cycled 20-times through a full range ofmotion.

Post-injection checks were made for any animal displaying signs ofdistress and discomfort, and additional analgesics were given if needed.All treatments were recorded in the appropriate study documentation.

D. Analysis

Blood Collection:

Blood was collected from each animal just prior to the start of thestudy, and at 5 hours post-injection and at days 1, 4, 7, 14 and 28 fromeach of the remaining animals. CBC and blood chemistry panels were runat each time point.

Necropsy:

Animals were humanely sacrificed at either 14 days or 28 days day postinitial injection with an intravenous injection consisting of Diazepam0.22 mg/kg and Ketamine 10 mg/kg for induction of general anesthesia.Following this, the anesthetized animals were given an IV overdose ofconcentrated potassium chloride (KCl) until the cardiac arrest had beenverified.

Gross Morphological Observations:

After collection of the knee joints, the joints were opened and grossevaluation as described in Table 2 of the injected stifle joints wasdone.

TABLE 9 Gross Evaluation and Sample Collection Gross Sample PhotographSample Evaluation Collection and Score Synovial Fluid (left and right) XX Left and Right Knee joints X X Left and Right posterior X X X synovialpouch Left and Right cartilage Sample X X X Left and Right popliteal X XX lymph node

Additionally, semi-quantitative grading of the joint by a singleobserver as outline in Table 3 was performed.

TABLE 10 Gross Evaluation Grading Scale Score Coloration Hyperemia Edema0 Normal None None 1 Slightly yellow Slight Slight 2 Yellow ModerateModerate 3 Marked Marked

The total joint gross evaluation score was the sum of the coloration,hyperemia, and edema scores (0-8 points).

Synovial Fluid Evaluation

After collection of the synovial fluid from the opened joints, the totalvolume was recorded. The fluid was grossly evaluated for viscosity,clarity and color and semi-quantitatively graded as per Table 11. With ahemocytometer, total white cell counts were done. Additionally, asynovial fluid smear was made for differential microscopic analysis. Anyremaining synovial fluid was preserved frozen in individually labeledcryovials at −80° C. A synovial fluid smear was retained for potentialfuture analysis.

TABLE 11 Description and Score for Synovial Fluid Score Color ClarityString 0 S = STRAW C = CLEAR N = NORMAL 1 P = PINK H = HAZY A = ABNORMAL2 Y = YELLOW/R = RED D = CLOUDY W = WATERY 3 B = BLOODY T = TURBID

Total synovial fluid score is the sum of the color, clarity and stringscores (08 points).

Histological Evaluation:

Immediately after dissection and following gross joint surfaceevaluation a sagital section of each joint was cut through the medialfemoral condyle (MFC). These sections were placed individually in 10%neutral buffered formalin. The fixed tissue was shipped by overnightcarrier to Premier Laboratories for processing. The right and left MFCsections were processed using standard histological techniques andstained with hematoxylin and eosin (H&E) and Safranin-O (SAF-O) with afast green counter stain. The slides from the MFC sections wereevaluated by the Mankin Scoring System for osteoarthritis as describedin Table 12.

TABLE 12 Modified Mankin Scoring System Structure Normal [0] SurfaceIrregularities [1] Pannus & Surface Irregularities [2] Clefts toTransitional Zone [3] Clefts to Radial Zone [4] Clefts to Calcified Zone[5] Complete Disorganization [6] Cells Normal [0] DiffuseHypercellularity [1] Cloning [2] Hypocellularity [3] Safranin-O StainingNormal [0] Slight Reduction [1] Moderate Reduction [2] Severe Reduction[3] No Dye Noted [4] Tidemark Integrity Intact [0] Crossed By BloodVessels [1] Maximal Score 14 (Normal = 0)

E. Results

The results of the Mankin scoring systems for the cartilage samples forthe joints treated with the various formulations are shown in Tables13a-h and are shown in FIG. 11. FIG. 9 (14 Days post-treatment) and 10(28 Days post treatment) show the safranin O stain score for cartilagesamples for the joints treated with the various formulations at 14 and28 Days post-treatment respectively.

TABLE 13a Mankin Score of Femoral Cartilage at 14 day evaluation, Group1 Safranin- Tide Mark Total Mankin Sample Treatment Structure Cells OStain Integrity Score 3256 HA-VS Gel 5 3 2 0 10 RFC 3171 HA-VS Gel 4 1 00 5 RFC 3831 HA-VS Gel 0 0 1 0 1 RFC MEAN 3.0 1.3 1.0 0.0 5.3 SD 2.6 1.51.0 0.0 4.5 3256 0.9% NaCl 4 1 2 0 7 LFC 3171 0.9% NaCl 4 1 0 0 5 LFC3831 0.9% NaCl 0 0 1 0 1 LFC MEAN 2.7 0.7 1.0 0.0 4.3 SD 2.3 0.6 1.0 0.03.1 MODIFIED MANKIN SCORING SYSTEM STRUCTURE Normal [0] SurfaceIrregularities [1] More Widespread Surface Irregularities [2] Clefts toTransitional Zone [3] Clefts to Radial Zone [4] Clefts to Calcified Zone[5] Complete Disorganization [6] CELLS Normal [0] Mild Focal toMultifocal Hypocellularity [1] Mild Focal to Multifocal Hypocellularitywith Cloning [2] Focally Extensive to Diffuse Hypocellularity [3]SAFRANIN-O STAINING Normal [0] Slight Reduction [1] Moderate Reduction[2] Severe Reduction [3] No Dye Noted [4] TIDEMARK INTEGRITY Intact [0]Crossed By Blood Vessels [1]

TABLE 13b Mankin Score of Femoral Cartilage at 14 day evaluation, Group2 Safranin- Tide Mark Total Mankin Sample Treatment Structure Cells OStain Integrity Score 3840 HA-VS/TA 3.0 1.0 2.0 0.0 6.0 RFC Gel 3596HA-VS/TA 0.0 0.0 3.0 0.0 3.0 RFC Gel 3174 HA-VS/TA 4.0 2.0 2.0 0.0 8.0RFC Gel MEAN 2.3 1.0 2.3 0.0 5.7 SD 2.1 1.0 0.6 0.0 2.5 3840 0.9% NaCl3.0 1.0 0.0 0.0 4.0 LFC 3596 0.9% NaCl 0.0 0.0 1.0 0.0 1.0 LFC 3174 0.9%NaCl 4.0 2.0 2.0 0.0 8.0 LFC MEAN 2.3 1.0 1.0 0.0 4.3 SD 2.1 1.0 1.0 0.03.5 MODIFIED MANKIN SCORING SYSTEM STRUCTURE Normal [0] SurfaceIrregularities [1] More Widespread Surface Irregularities [2] Clefts toTransitional Zone [3] Clefts to Radial Zone [4] Clefts to Calcified Zone[5] Complete Disorganization [6] CELLS Normal [0] Mild Focal toMultifocal Hypocellularity [1] Mild Focal to Multifocal Hypocellularitywith Cloning [2] Focally Extensive to Diffuse Hypocellularity [3]SAFRANIN-O STAINING Normal [0] Slight Reduction [1] Moderate Reduction[2] Severe Reduction [3] No Dye Noted [4] TIDEMARK INTEGRITY Intact [0]Crossed By Blood Vessels [1]

TABLE 13c Mankin Score of Femoral Cartilage at 14 day evaluation, Group3 Safranin- Tide Mark Total Mankin Sample Treatment Structure Cells OStain Integrity Score 3833 Triamcinolone 4.0 1.0 3.0 0.0 8.0 RFCAcetonide 2 mg/ml 3133 Triamcinolone 0.0 0.0 4.0 0.0 4.0 RFC Acetonide 2mg/ml 3177 Triamcinolone 4.0 1.0 2.0 0.0 7.0 RFC Acetonide 2 mg/ml MEAN2.7 0.7 3.0 0.0 6.3 SD 2.3 0.6 1.0 0.0 2.1 3833 0.9% NaCl 0.0 0.0 1.00.0 1.0 LFC 3133 0.9% NaCl 0.0 0.0 2.0 0.0 2.0 LFC 3177 0.9% NaCl 0.00.0 1.0 0.0 1.0 LFC MEAN 0.0 0.0 1.3 0.0 1.3 SD 0.0 0.0 0.6 0.0 0.6MODIFIED MANKIN SCORING SYSTEM STRUCTURE Normal [0] SurfaceIrregularities [1] More Widespread Surface Irregularities [2] Clefts toTransitional Zone [3] Clefts to Radial Zone [4] Clefts to Calcified Zone[5] Complete Disorganization [6] CELLS Normal [0] Mild Focal toMultifocal Hypocellularity [1] Mild Focal to Multifocal Hypocellularitywith Cloning [2] Focally Extensive to Diffuse Hypocellularity [3]SAFRANIN-O STAINING Normal [0] Slight Reduction [1] Moderate Reduction[2] Severe Reduction [3] No Dye Noted [4] TIDEMARK INTEGRITY Intact [0]Crossed By Blood Vessels [1]

TABLE 13d Mankin Score of Femoral Cartilage at 14 day evaluation, Group4 Safranin- Tide Mark Total Mankin Sample Treatment Structure Cells OStain Integrity Score 3593 Triamcinolone 0.0 0.0 4.0 0.0 4.0 RFCAcetonide 8 mg/ml 3849 Triamcinolone 5.0 1.0 3.0 0.0 9.0 RFC Acetonide 8mg/ml 3589 Triamcinolone 0.0 0.0 3.0 0.0 3.0 RFC Acetonide 8 mg/ml MEAN1.7 0.3 3.3 0.0 5.3 SD 2.9 0.6 0.6 0.0 3.2 3593 0.9% NaCl 0.0 0.0 2.00.0 2.0 LFC 3849 0.9% NaCl 1.0 1.0 2.0 0.0 4.0 LFC 3589 0.9% NaCl 0.00.0 3.0 0.0 3.0 LFC MEAN 0.3 0.3 2.3 0.0 3.0 SD 0.6 0.6 0.6 0.0 1.0MODIFIED MANKIN SCORING SYSTEM STRUCTURE Normal [0] SurfaceIrregularities [1] More Widespread Surface Irregularities [2] Clefts toTransitional Zone [3] Clefts to Radial Zone [4] Clefts to Calcified Zone[5] Complete Disorganization [6] CELLS Normal [0] Mild Focal toMultifocal Hypocellularity [1] Mild Focal to Multifocal Hypocellularitywith Cloning [2] Focally Extensive to Diffuse Hypocellularity [3]SAFRANIN-O STAINING Normal [0] Slight Reduction [1] Moderate Reduction[2] Severe Reduction [3] No Dye Noted [4] TIDEMARK INTEGRITY Intact [0]Crossed By Blood Vessels [1]

TABLE 13e Mankin Score of Femoral Cartilage at 28 day evaluation, Group5 Safranin- Tide Mark Total Mankin Sample Treatment Structure Cells OStain Integrity Score 3267 HA-VS Gel 1 1 1 0 3 RFC 3837 HA-VS Gel 3 1 30 7 RFC* 3595 HA-VS Gel 1 1 1 0 3 RFC MEAN 1.0 1.0 1.0 0.0 3.0 SD 0.00.0 0.0 0.0 0.0 3267 0.9% NaCl 1 1 1 0 3 LFC 3837 0.9% NaCl 3 1 3 0 7LFC* 3595 0.9% NaCl 1 1 2 0 4 LFC MEAN 1.0 1.0 1.5 0.0 3.5 SD 0.0 0.00.7 0.0 0.7 *Animal died prematurely. Data recorded but not included inaverages. MODIFIED MANKIN SCORING SYSTEM STRUCTURE Normal [0] SurfaceIrregularities [1] More Widespread Surface Irregularities [2] Clefts toTransitional Zone [3] Clefts to Radial Zone [4] Clefts to Calcified Zone[5] Complete Disorganization [6] CELLS Normal [0] Mild Focal toMultifocal Hypocellularity [1] Mild Focal to Multifocal Hypocellularitywith Cloning [2] Focally Extensive to Diffuse Hypocellularity [3]SAFRANIN-O STAINING Normal [0] Slight Reduction [1] Moderate Reduction[2] Severe Reduction [3] No Dye Noted [4] TIDEMARK INTEGRITY Intact [0]Crossed By Blood Vessels [1]

TABLE 13f Mankin Score of Femoral Cartilage at 28 day evaluation, Group6 Safranin- Tide Mark Total Mankin Sample Treatment Structure Cells OStain Integrity Score 3264 HA-VS/TA 0.0 0.0 3.0 0.0 3.0 RFC Gel 3587HA-VS/TA 5.0 2.0 2.0 0.0 9.0 RFC Gel 3173 HA-VS/TA 0.0 0.0 2.0 0.0 2.0RFC Gel MEAN 1.7 0.7 2.3 0.0 4.7 SD 2.9 1.2 0.6 0.0 3.8 3264 0.9% NaCl0.0 0.0 0.0 0.0 0.0 LFC 3587 0.9% NaCl 5.0 2.0 1.0 0.0 8.0 LFC 3173 0.9%NaCl 0.0 0.0 1.0 0.0 1.0 LFC MEAN 1.7 0.7 0.7 0.0 3.0 SD 2.9 1.2 0.6 0.04.4 MODIFIED MANKIN SCORING SYSTEM STRUCTURE Normal [0] SurfaceIrregularities [1] More Widespread Surface Irregularities [2] Clefts toTransitional Zone [3] Clefts to Radial Zone [4] Clefts to Calcified Zone[5] Complete Disorganization [6] CELLS Normal [0] Mild Focal toMultifocal Hypocellularity [1] Mild Focal to Multifocal Hypocellularitywith Cloning [2] Focally Extensive to Diffuse Hypocellularity [3]SAFRANIN-O STAINING Normal [0] Slight Reduction [1] Moderate Reduction[2] Severe Reduction [3] No Dye Noted [4] TIDEMARK INTEGRITY Intact [0]Crossed By Blood Vessels [1]

TABLE 13g Mankin Score of Femoral Cartilage at 28 day evaluation, Group7 Safranin- Tide Mark Total Mankin Sample Treatment Structure Cells OStain Integrity Score 3592 Triamcinolone 4.0 3.0 3.0 0.0 10.0 RFCAcetonide 2 mg/ml 3591 Triamcinolone 0.0 2.0 4.0 0.0 6.0 RFC Acetonide 2mg/ml 3594 Triamcinolone 4.0 2.0 3.0 0.0 9.0 RFC Acetonide 2 mg/ml MEAN2.7 2.3 3.3 0.0 8.3 SD 2.3 0.6 0.6 0.0 2.1 3592 0.9% NaCl 4.0 1.0 1.00.0 6.0 LFC 3591 0.9% NaCl 1.0 1.0 1.0 0.0 3.0 LFC 3594 0.9% NaCl 2.01.0 1.0 0.0 4.0 LFC MEAN 2.3 1.0 1.0 0.0 4.3 SD 1.5 0.0 0.0 0.0 1.5MODIFIED MANKIN SCORING SYSTEM STRUCTURE Normal [0] SurfaceIrregularities [1] More Widespread Surface Irregularities [2] Clefts toTransitional Zone [3] Clefts to Radial Zone [4] Clefts to Calcified Zone[5] Complete Disorganization [6] CELLS Normal [0] Mild Focal toMultifocal Hypocellularity [1] Mild Focal to Multifocal Hypocellularitywith Cloning [2] Focally Extensive to Diffuse Hypocellularity [3]SAFRANIN-O STAINING Normal [0] Slight Reduction [1] Moderate Reduction[2] Severe Reduction [3] No Dye Noted [4] TIDEMARK INTEGRITY Intact [0]Crossed By Blood Vessels [1]

TABLE 13h Mankin Score of Femoral Cartilage at 28 day evaluation, Group8 Safranin- Tide Mark Total Mankin Sample Treatment Structure Cells OStain Integrity Score 3588 Triamcinolone 4.0 3.0 3.0 0.0 10.0 RFC*Acetonide 8 mg/ml 3590 Triamcinolone 5.0 3.0 4.0 0.0 12.0 RFC Acetonide8 mg/ml 3162 Triamcinolone 1.0 1.0 4.0 0.0 6.0 RFC Acetonide 8 mg/mlMEAN 3.0 2.0 4.0 0.0 9.0 SD 2.8 1.4 0.0 0.0 4.2 3588 0.9% NaCl 4.0 3.03.0 0.0 10.0 LFC* 3590 0.9% NaCl 3.0 1.0 2.0 0.0 6.0 LFC 3162 0.9% NaCl3.0 1.0 2.0 0.0 6.0 LFC MEAN 3.0 1.0 2.0 0.0 6.0 SD 0.0 0.0 0.0 0.0 0.0*Animal died prematurely. Data recorded but not included in averages.MODIFIED MANKIN SCORING SYSTEM STRUCTURE Normal [0] SurfaceIrregularities [1] More Widespread Surface Irregularities [2] Clefts toTransitional Zone [3] Clefts to Radial Zone [4] Clefts to Calcified Zone[5] Complete Disorganization [6] CELLS Normal [0] Mild Focal toMultifocal Hypocellularity [1] Mild Focal to Multifocal Hypocellularitywith Cloning [2] Focally Extensive to Diffuse Hypocellularity [3]SAFRANIN-O STAINING Normal [0] Slight Reduction [1] Moderate Reduction[2] Severe Reduction [3] No Dye Noted [4] TIDEMARK INTEGRITY Intact [0]Crossed By Blood Vessels [1]

In the cartilage at Day 28 there was no difference in the modifiedMankin scores for HA-VS-PEG-(SH)₂ gel compared to its control. There wasa mild increase in the loss of Safranin O staining intensity portion ofthe modified Mankin score for Groups 7 and 8 compared to either Groups 5or 6. From Day 14 to Day 28 there was an increase in the modified Mankinscores of both Triamcinolone Acetonide-alone-treated groups (Groups 7and 8). Such an increase in these scores over time is not observed forthe HA-VS-PEG-(SH)₂ gel-treated Group 5 or the HA-VS-PEG-(SH)₂-TA geltreated Group 6.

The results of this study show there are no local or systemic effects at28 days after intra-articular injection of 1.5 ml of the HA-VS-PEG-(SH)₂alone or combined with 2 mg/ml of Triamcinolone Acetonide,HA-VS-PEG-(SH)₂-TA, into the knee joint of a goat. The effect on thecartilage of the addition of the triamcinolone acetonide to theHA-VS-PEG-(SH)₂ gel was less than the effect of injecting an equivalentdose or a higher dose of the triamcinolone acetonide alone.

The glycosaminoglycan specific staining with Safranin-O demonstratedthat the effect of triamcinolone acetonide at 2 mg/mL (3 mg) whenformulated in the HA-VS-PEG-(SH)₂ gel on the cartilage was lower thanboth the 2 mg/mL (3 mg) and 8 mg/mL (12 mg) bolus dose of triamcinoloneacetonide at the 14 day and 28 day time points.

FIGS. 12 and 13 illustrate representative medial femoral condylehistology with Safranin-O staining (40×) at Day 14 (FIG. 12) and Day 28(FIG. 13) post-injection. The figures show that there is more safranin-Ostaining for the cartilage sample from the joints treated with thetriamcinolone acetonide incorporated into the hydrogel than for thecartilage sample treated with an equivalent dose of triamcinoloneacetonide that was injected directly into the joint (i.e. notincorporated into a hydrogel).

Example 35 Measurement of Extrusion Force

The force required to extrude the HA-VS/PEG-(SH)₂/HA product (Example 5,Example 41) and the HA-VS/PEG-(SH)₂/HA with triamcinilone acetonide(Example 38) was measured using a Chatillon motorized force tester(Chatillon LTCM-6 motorized tester with a Chatillon DFE-025 digitalforce gauge, Ametec TCI Division). A fixture to hold a 10 mL syringe wasattached to the base plate of the motorized tester such that the forcegauge was directly over the plunger rod of the syringe. The force testerwas turned on and the travel speed was set to 3 inches per minute byadjusting the rotary speed control dial to “3”. The motorized tester armwas moved to its upper most point. The end-cap of the 10 mL glasssyringe that contained the formulation to be tested was removed and a 21gauge needle was attached to the uncapped luer end tip. The syringe asplaced in the syringe holder and the motorized tester arm was movedslowly downwards until the force gauge lightly touched the syringeplunger rod. A 16 mL test tube was placed under the end of the 21 gaugeneedle. The force gauge was set to record the maximum force. The forcegauge was zeroed. The toggle switch of the motorized tested was thenpressed such that the plunged of the syringe was depressed and thecontents of the syringe were extruded through the 21 gauge needle. Themotorized tester was stopped just prior to syringe stopper reaching thebottom of the syringe. The maximum extrusion force displayed on theforce gauge screen was recorded. The results from the variousformulations tested are shown below:

TABLE 14 Extrusion Force (lbs) HA-VS/PEG-(SH)₂ HA-VS/PEG-(SH)₂HA-VS/PEG-(SH)₂/ Sample with HA (Lot with HA (Lot TA with HA (Lot #NB30:16) M0229) M0231) 1 6.9 10.52 6.06 2 7.9 10.21 7.78 3 6.1 10.368.14 4 7.2 5 6.9 6 7.3 Average 7.1 10.36 7.33 STD 0.6 0.16 1.11

Example 36 Stability of Extrusion Force of HA-VS/PEG-(SH)₂ with HA OverTime

The force required to extrude the HA-VS/PEG-(SH)₂/HA product (example 5)as a function of time was measured using a Chatillon motorized forcetester (Chatillon LTCM-6 motorized tester with a Chatillon DFE-025digital force gauge, Ametec TCI Division). The extrusion force wasmeasured after the product was made and then at 1 month and 3 monthsafter that initial measurement. The samples were stored at roomtemperature over the 3 month time period. The extrusion force wasmeasured for each sample as follows: A fixture to hold a 10 mL syringewas attached to the base plate of the motorized tester such that theforce gauge was directly over the plunger rod of the syringe. The forcetester was turned on and the travel speed was set to 3 inches per minuteby adjusting the rotary speed control dial to “3”. The motorized testerarm was moved to its upper most point. The end-cap of the 10 mL glasssyringe that contained the formulation to be tested was removed and a 21gauge needle was attached to the uncapped luer end tip. The syringe asplaced in the syringe holder and the motorized tester arm was movedslowly downwards until the force gauge lightly touched the syringeplunger rod. A 16 mL test tube was placed under the end of the 21 gaugeneedle. The force gauge was set to record the maximum force. The forcegauge was zeroed. The toggle switch of the motorized tested was thenpressed such that the plunged of the syringe was depressed and thecontents of the syringe were extruded through the 21 gauge needle. Themotorized tester was stopped just prior to syringe stopper reaching thebottom of the syringe. The maximum extrusion force displayed on theforce gauge screen was recorded. The results for Lot NB30:16 are shownbelow and show that there is no real change in the force required toextrude the product through a 21 gauge needle over 3 months.

TABLE 15 Extrusion Force (lbs) Sample # T = 0 T = 1 month T = 3 months 110.31 6.87 9.46 2 8.7 7.62 7.14 3 8.72 10.55 11.57 4 9.47 7.53 7.36 510.43 8.25 7.65 6 9.63 8.3 8.95 Average 9.54 8.19 8.69 STD 0.75 1.271.69

Example 37 Preparation of HA-VS/PEG-(SH)2/TA Gel with HA

170.8 mg, 341.3 mg, 511.7 mg, and 682.7 mg sterile triamcinoloneacetonide were weighted out in 4 separate sterile 125 mL plasticbottles, which were labeled as TA 10 mg, TA 20 mg, TA 30 mg, and TA 40mg, respectively. Each bottle containing the TA was tared on a balanceand 14.98 g, 14.99 g, 14.99 g, and 15.01 g of sterile filtered (filteredthrough 0.2 urn sterile filters, PVDF membrane) 14 mg/mL HA-VS in waterwere added to each of the 4 bottles in the order of TA 10 mg to 40 mg.TA powder and HA-VS solution were mixed by stirring until the resultantsolutions appeared visually homogeneous. 0.375 mL of sterile filtered(through 0.2 um sterile filter) 1M Sodium Phosphate, pH 7.4, was addedto each of the bottles, and the resultant mixtures were mixed well.0.543 mL of 50 mg/mL of PEG-dithiol 3350 [PEG(SH)₂] (sterile filteredthrough 0.2 um sterile filter) was added to each container and mixthoroughly. The above steps were performed in a biohood. The mixtureswere placed in a 37° C. oven overnight. The formulations were removedfrom the oven, the exterior of the containers were wiped down with 70/30IPA/water and then transferred into a biohood. Each gel was broken upusing a sterile spatula. 86.23 g, 86.25 g, 86.40 g, and 86.23 g of 7.83mg/mL of HA in 0.9% saline (filtered through 0.2 um sterile filter, PVDFmembrane) was added to the containers labeled TA 10 mg, 20 mg, 30 mg,and 40 mg, respectively. Each mixture was allowed to swell at roomtemperature for 3 hours. Each mixture was then passed through a 0.85 ummesh in a filter housing [A 23 mm diameter disc of a polyester mesh(McMaster Carr, Cat #9218T13, Mesh Size: 20.3×20.3, Square/RectangleSize: 0.0331″, Micron Rating: 840 Microns, Percentage of Open Area: 46,Thread Diameter: 0.0157″) was cut out using a 23 mm leather punch. Thedisc was inserted into a 25 mm syringe filter holder (Cole Palmer, Cat #EW-29550-42) and the filter holder was closed. The filter holder thatcontained the mesh was autoclaved]. The collected meshed mixture wasthen passed through a 0.85 um mesh for a second time. The collectedmixture was then stored in a plastic container.

Example 38 Packaging of HA-VS/PEG-(SH)₂/TA Gel with HA

6 mL of each formulation from Example 37 was then aliquoted into a 10 mLglass syringe (BD Hypak glass syringe, P/N 47262119) that had a syringecap. A plunger rod was screwed into the back of a sterile stopper (BD,P/N 47318319) after which the stopper/plunger was inserted into the neckof the syringe. The syringe was inverted and the syringe cap was opensslightly. The plunger was depressed until the excess air was expelled.The syringe cap was then tightened. The above steps were performed in abiohood. The process was repeated until all the product was packaged.

Example 39 Determining Particle Size—Deionized Water Wash

Stainless steel sieves of 2.36 mm (USA standard test sieve #8), 1.4 mm(USA standard test sieve #14), 1 mm (USA standard test sieve #18), 0.85mm (USA standard test sieve #20), 0.6 mm (USA standard test sieve #30),0.425 mm (USA standard test sieve #40), 0.25 mm (USA standard test sieve#60), and 0.150 mm (USA standard test sieve #100) were washed with DIwater, and wiped dry using Kimwipes. After measuring the weight of eachsieve, the sieves was placed on top of another going from the smallestsize (#100) on the bottom to the largest size (#8) at the top. 100 mL ofthe HA-VS/PEG-(SH)₂/TA with HA formulation (Example 37) was slowlypoured into the top sieve. Once most of the liquid component of thesample had passed through the top sieve, approx. 50 mL deionized waterwas slowly added to the top sieve to rinse the gel component that wasretained by that sieve. Once the liquid component has passed through thesieve, the sieve was removed from the stack. This process was repeateduntil each sieve had been washed and removed from the stack. Excesswater droplets that remained on each sieve was wiped away using a papertowel. The total weight of each sieve (sieve plus collected gel) wasmeasured. The weight of gel particles collected on each sieve wascalculated by subtracting the initial sieve weight from the total sieveweight. The percentage gel collected by each sieve was calculated bytaking the weight of gel collected on a particular sieve and thendividing by the total weight of the gel collected by all the sieves.

TABLE 16 Sieve Gel collected in Sieve size each sieve (%) size # (mm) TA10 TA 20 TA 30 TA 40 8 2.36 0.1 0.3 0.5 0.0 14 1.40 11.4 14.7 19.4 7.618 1.00 44.9 48.0 34.2 35.2 20 0.85 29.4 23.1 22.0 28.0 30 0.60 7.4 7.814.7 14.7 40 0.425 3.7 2.7 4.4 7.8 60 0.25 1.5 1.7 2.9 4.2 100 0.15 1.71.7 2.0 2.6

Example 40 Determining Particle Size—Saline Wash

Stainless steel sieves of 2.36 mm (USA standard test sieve #8), 1.4 mm(USA standard test sieve #14), 1 mm (USA standard test sieve #18), 0.85mm (USA standard test sieve #20), 0.6 mm (USA standard test sieve #30),0.425 mm (USA standard test sieve #40), 0.25 mm (USA standard test sieve#60), and 0.150 mm (USA standard test sieve #100) were washed with DIwater, and wiped dry using Kimwipes. After measuring the weight of eachsieve, the sieves was placed on top of another going from the smallestsize (#100) on the bottom to the largest size (#8) at the top. 100 mL ofthe HA-VS/PEG-(SH)₂/TA with HA (TA 10) formulation (Example 37) wasslowly poured into the top sieve. Once most of the liquid component ofthe sample had passed through the top sieve, approx. 50 mL 0.9% salinewas slowly added to the top sieve to rinse the gel component that wasretained by that sieve. Once the liquid component has passed through thesieve, the sieve was removed from the stack. This process was repeateduntil each sieve had been washed and removed from the stack. Excesssaline droplets that remained on each sieve was wiped away using a papertowel. The total weight of each sieve (sieve plus collected gel) wasmeasured. The weight of gel particles collected on each sieve wascalculated by subtracting the initial sieve weight from the total sieveweight. The percentage gel collected by each sieve was calculated bytaking the weight of gel collected on a particular sieve and thendividing by the total weight of the gel collected by all the sieves.

TABLE 17 Sieve Sieve Gel collected in each sieve (%) size # size (mm)Run-1 Run-2 Run-3 Ave SD 8 2.36 0.0 0.4 0.7 0.4 0.3 14 1.40 9.0 3.4 10.57.6 3.8 18 1.00 50.6 50.1 48.8 49.9 0.9 20 0.85 20.5 23.2 18.6 20.8 2.330 0.60 10.9 12.8 10.9 11.6 1.1 40 0.425 4.8 5.2 5.7 5.3 0.4 60 0.25 2.73.5 3.1 3.1 0.4 100 0.15 1.3 1.1 1.7 1.4 0.3

Example 41 HA-VS/PEG-(SH)2 Gel Slurry with Hyaluronic Acid—HA Swelling

Three of sterile 125 mL bottles were tared on a balance separately, and14.97 g, 14.95 g, and 15.00 g of 14 mg/mL HA-VS in water (filteredthrough a 0.2 um sterile filter, PVDF membrane) were added to each ofthe three bottles. 0.375 mL of 1M Sodium Phosphate, pH 7.4 (sterilefiltered through 0.2 um sterile filter) was added to each of thebottles, and mixed well. 0.543 mL of 50 mg/mL of PEG(SH)2 (sterilefiltered through 0.2 um sterile filter) was added to each container andmix thoroughly. The above steps were performed in a biohood. Themixtures were placed in a 37° C. oven overnight. The formulations wereremoved from the oven, the exterior of the containers were wiped downwith 70/30 IPA/water and then transferred into a biohood. Each gel wasbroken up with a sterile spatula. Then 86.40 g, 86.21 g, and 86.31 g of7.83 mg/mL of HA in 0.9% saline (filtered through a 0.2 um sterilefilter, PVDF membrane) was added to the containers. The gels wereswelled at room temperature for 3 hours. Each mixture was then passedthrough a 0.85 um mesh in a filter housing [A 23 mm diameter disc of apolyester mesh (McMaster Carr, Cat #9218T13, Mesh Size: 20.3×20.3,Square/Rectangle Size: 0.0331″, Micron Rating: 840 Microns, Percentageof Open Area: 46, Thread Diameter: 0.0157″) was cut out using a 23 mmleather punch. The disc was inserted into a 25 mm syringe filter holder(Cole Palmer, Cat # EW-29550-42) and the filter holder was closed. Thefilter holder that contained the mesh was autoclaved.]. The collectedmeshed mixture was then passed through a 0.85 um mesh for a second time.The collected mixture was then stored in a plastic container.

Example 42 Packaging of HA-VS/PEG-(SH)₂ Gel Slurry with Hyaluronic Acid

6 mL of each formulation from Example 41 was then aliquoted into a 10 mLglass syringe (BD Hypak glass syringe, P/N 47262119) that had a syringecap. A plunger rod was screwed into the back of a sterile stopper (BD,P/N 47318319) after which the stopper/plunger was inserted into the neckof the syringe. The syringe was inverted and the syringe cap was opensslightly. The plunger was depressed until the excess air was expelled.The syringe cap was then tightened. The above steps were performed in abiohood. The process was repeated until all the product was packaged.

Example 43 Determining Particle Size—Saline Wash

Stainless steel sieves of 2.36 mm (USA standard test sieve #8), 1.4 mm(USA standard test sieve #14), 1 mm (USA standard test sieve #18), 0.85mm (USA standard test sieve #20), 0.6 mm (USA standard test sieve #30),0.425 mm (USA standard test sieve #40), 0.25 mm (USA standard test sieve#60), and 0.150 mm (USA standard test sieve #100) were washed with DIwater, and wiped dry using Kimwipes. After measuring the weight of eachsieve, the sieves were placed on top of another going from the smallestsize (#100) on the bottom to the largest size (#8) at the top. 100 mL ofthe HA-VS/PEG-(SH)₂ gel slurry with hyaluronic acid formulation (Example41) was slowly poured into the top sieve. Once most of the liquidcomponent of the sample had passed through the top sieve, approx. 50 mL0.9% saline was slowly added to the top sieve to rinse the gel componentthat was retained by that sieve. Once the liquid component has passedthrough the sieve, the sieve was removed from the stack. This processwas repeated until each sieve had been washed and removed from thestack. Excess saline droplets that remained on each sieve was wiped awayusing a paper towel. The total weight of each sieve (sieve pluscollected gel) was measured. The weight of gel particles collected oneach sieve was calculated by subtracting the initial sieve weight fromthe total sieve weight. The percentage gel collected by each sieve wascalculated by taking the weight of gel collected on a particular sieveand then dividing by the total weight of the gel collected by all thesieves.

TABLE 18 Sieve Sieve Gel collected in each sieve (%) Size # size (mm)Run-1 Run-2 Run-3 Ave SD 8 2.36 2.2 2.5 2.0 2.3 0.3 14 1.40 9.7 9.8 9.29.6 0.3 18 1.00 33.2 29.1 27.2 29.8 3.1 20 0.85 25.4 22.1 24.9 24.1 1.830 0.60 14.4 19.1 19.1 17.5 2.7 40 0.425 10.0 8.5 10.3 9.6 1.0 60 0.253.4 5.7 5.1 4.7 1.2 100 0.15 1.8 3.1 2.3 2.4 0.7

Example 44 Sterility and Endotoxin Testing

The HA-VS/PEG-(SH)₂ gel with HA (Example 42, Example 5) andHA-VS/PEG-(SH)₂/TA gel with HA (Example 37, TA10) were tested forsterility and endotoxins by WuXi AppTec using protocol # BS210CBY.203and BE215CBY.203 respectively. All the samples were sterile and hadendotoxin levels of <0.5 EU/mL.

Example 45 In Vivo Biocompatibility Testing of HA-VS/PEG-(SH)₂ with HA

The following in-vivo study was undertaken to examine the in-vivobiocompatibility of the test material relative to a commerciallyavailable viscosupplement product in goats.

Materials used for study:

Test Material: Hydros—HA-VS/PEG-(SH)₂ with HA [Lot NB51:119]

Control Material: Synvisc—Commercially available viscosupplement product

A total of 6 skeletally mature female goats were used for this study.They were acquired from an approved USDA source. Animals weighed between65 to 99 lbs at the start of the study. Goats were determined to beCaprine Arthritis Encephalitis (CAE) and Johne's negative prior to beingplaced in this study. Each animal was given a general health evaluation(subject to visual observation for attitude, ease in respiration, andfreedom from diarrhea and nasal discharge) by a qualified veterinarianprior to being placed in the study. The animals were examined for anyevidence of disease or lameness. Acceptability into the study wascontingent on being disease free, clinically sound, and no history ofprior use of the stifle joint. The goats were conditioned for anappropriate period of time as determined by the institution. Animalhousing conditions conformed with applicable laws and regulationsrelating to laboratory animals, i.e., Animal Welfare Act, Public Law89-544 as amended in Public Law 99-198, Federal Register 52:16, UnitedStates Department of Agriculture-Animal and Plant Inspection Service(USDA-APHIS), 1985 and Public Health Service Policy on Humane Care ofLaboratory Animals, Office for Protection Against ResearchRisks/National Institutes of Health (OPRR/NIH), September, 1986. Thegoats were maintained in large indoor runs (pens) following injection.The goats had unrestricted activity at all times. All animals receivedapproximately 2 lbs. of small ruminant diet per day as well as loosehay. Tap water was provided ad libitum. Feed was withheld approximately12-24 hours prior to anesthesia and water was withheld approximately 12hours prior to injections. A unique ear tag identified each animal.

Treatment

The study was designed as follows.

TABLE 19 Group and Treatment Assignment Sacrifice Ear Right Stifle LeftStifle Time after Group Tag (1.5 ml) (1.5 ml) R/L injection 1A 3750 TestMaterial Control Material 24 ± 1 hours Hydros Test Material Synvisc 1A3751 Test Material Control Material 24 ± 1 hours Hydros Test MaterialSynvisc 1A 3752 Test Material Control Material 24 ± 1 hours Hydros TestMaterial Synvisc 1B 3597 Control Material Test Material 24 ± 1 hoursSynvisc Hydros Test Material 1B 3753 Control Material Test Material 24 ±1 hours Synvisc Hydros Test Material 1B 3754 Control Material TestMaterial 24 ± 1 hours Synvisc Hydros Test Material Total 6

The basic injection procedure was identical for all subjects. Allinjections were performed under strict asepsis. The animals wereanesthetized with an intravenous injection of Diazepam (0.1-0.5 mg/kg)and Ketamine (4.4-7.5 mg/kg) to effect. Each knee was physicallyexamined for drawer, range of motion, swelling, temperature, crepitus,patella tracking, and valgus/varus abnormalities. All injections wereconducted utilizing routine aseptic techniques. The left and rightstifles were prepared for injection by clipping the areas, thencleansing them with chlorohexidine scrub. The animal was placed indorsal recumbency. The right stifle was cleansed with chlorohexidinescrub alternating with 70% isopropyl alcohol three times and paintedwith iodine solution.

A standard technique was used to inject each stifle joint. A 2-inch by21-gauge sized sterile needle was introduced into the intra-articularspace via an anteromedial approach. The lateral intercondylar notch wallof the medial femoral condyle was felt and the needle backed slightlyoff. 1.5 ml of the Test Material was injected into the right joint forGroup 1A or 1.5 ml of the Control Material for Group 1B. The injectionneedle was removed and pressure was maintained on the injection site.The injected stifle joint was then cycled 20-times through a full rangeof motion. Immediately following this, the left stifle joint wascleansed with chlorohexidine scrub alternating with 70% isopropylalcohol three times and painted with iodine solution and 1.5 ml of theControl Material for Group 1A or 1.5 ml of the Test Material for Group1B was injected into the left stifle joint in a similar manner asdescribed above for the right stifle. The injection needle was removedand pressure maintained on the injection site. The injected stifle jointwas then cycled 20-times through a full range of motion.

Post-injection checks were made for any animal displaying signs ofdistress and discomfort, and additional analgesics were given if needed.All treatments were recorded in the appropriate study documentation.

Animals were humanely sacrificed at 24±1 hours post initial injectionwith an intravenous injection consisting of Diazepam 0.22 mg/kg andKetamine 10 mg/kg for induction of general anesthesia. Following this,the anesthetized animals were given an IV overdose of concentratedpotassium chloride (KCl) until the cardiac arrest had been verified.

Analysis

Gross Morphological Observations

After collection of the knee joints, the joints were opened and grossevaluation as described in Table 20 of the injected stifle joints wasdone. Photodocumentation was performed. Degenerative joint changes werenot evaluated.

TABLE 20 Gross Evaluation and Sample Collection Gross Sample PhotographSample Evaluation collection and/or Score Synovial Fluid (left andright) X X Left and Right Knee joints X X Left and Right synovium X XAdditionally, semi-quantitative grading of the joint by a singleobserver as outline in Table 21 was performed.

TABLE 21 Gross Joint Evaluation Grading Scale Score Coloration HyperemiaEdema 0 Normal None None 1 Slightly yellow Slight Slight 2 YellowModerate Moderate 3 Marked MarkedThe total joint gross evaluation score was the sum of the coloration,hyperemia, and edema scores (0-8 points).Synovial Fluid Evaluation

After collection of the synovial fluid from the opened joints, the totalvolume was recorded. The fluid was grossly evaluated for viscosity,clarity and color and semi-quantitatively graded as per Table 22. With ahemocytometer, total white cell counts were done. Additionally, asynovial fluid smear was made for differential microscopic analysis.Remaining synovial fluid was preserved frozen in individually labeledcryovials at −80° C. A synovial fluid smear was retained for potentialfuture analysis.

TABLE 22 Description and Score for Synovial Fluid Score Color ClarityString 0 S = STRAW C = CLEAR N = NORMAL 1 P = PINK H = HAZY A = ABNORMAL2 Y = YELLOW/R = RED D = CLOUDY W = WATERY 3 B = BLOODY T = TURBID

Total synovial fluid score is the sum of the color, clarity and stringscores (0-8 points).

Results

The tables below, along with FIG. 14, show that the HA-VS/PEG-(SH)₂ withHA is biocompatible in the joint at 24 hrs in the goat model.

TABLE 23 Synovial Fluid and Joint Gross Scores Evaluations (Sortedrelative to Test Material (TM) and Control Material) Total color; TotalGrand Ear Test Joint Vol- clarity; Synovial Total Tag Group ArticleScore ume string Fluid Score Score 3750 1A TM 0 1.6 SHN 1 1 3751 1A TM 01.4 SHN 1 1 3752 1A TM 0 1 SHN 1 1 3597 1B TM 0 1.1 SHN 1 1 3753 1B TM 00.75 PHN 2 2 3754 1B TM 0 0.45 SHN 1 1 mean 0.0 1.1 1.2 1.2 sd 0.0 0.40.4 0.4 3597 1B Control 0 2.2 SHN 1 1 3753 1B Control 0 1.9 PHN 2 2 37541B Control 0 1.5 SHN 1 1 3750 1A Control 0 1.3 SHN 1 1 3751 1A Control 00.8 SHN 1 1 3752 1A Control 1 1.85 SHN 1 2 mean 0.2 1.6 1.2 1.3 sd 0.40.5 0.4 0.5 Color: S = straw colored (0), Y = yellow (2), P = pink (1),R = red (2), B = bloody (3) Clarity: C = clear (0), H = hazy (1), D =cloudy (2) String (viscosity): N = normal (0), A = abnormal (1), W =watery (2) TM = Test Material

TABLE 24 Synovial fluid cell differential and leukocyte (WBC) countPercent Cells in Synovial Fluid TM with Macro/mono Ear Test WBC/ % % % %% TM surface Phagocytosis Absolute Tag Group Material mm³ PMNLymphocytes Monocytes Eosinophils Basophils present cells of TM WBC 37501A TM 23,890 82 0 18 0 0 + + v few + 38,224,000 3751 1A TM 7,210 90 0 100 0 + + v few + 10,094,000 3752 1A TM 7,127 89 2 9 0 0 + + v few +7,127,000 3597 1B TM 6,922 77 4 19 0 0 + + v few + 7,614,200 3753 1B TM3,789 74 3 23 0 0 + + v few + 2,841,750 3754 1B TM 2,200 63 3 34 0 0 + +v few + 990,000 mean 8,523 79.2 2.0 18.8 0.0 0.0 11,148,492 sd 7,80710.1 1.7 9.2 0.0 0.0 13,675,201 3750 1A Control 22,409 71 7 22 0 0 + +mod + 29,131,700 3751 1A Control 7,830 87 5 8 0 0 + + many + 6,264,0003752 1A Control 26,700 72 2 26 0 0 + + many + 49,395,000 3597 1B Control6,130 74 2 24 0 0 + + mod + 13,486,000 3753 1B Control 5,467 53 5 41 10 + + many + 10,387,300 3754 1B Control 8,100 53 2 45 0 0 + + many +12,150,000 mean 12,773 68.3 3.8 27.7 0.2 0.0 20,135,667 sd 9,280 13.22.1 13.5 0.4 0.0 16,324,705 (Sorted relative to Test Material (TM) andControl Material) PMN = polymorphonuclear leukocytes WBC = White BloodCells TM = Test Material

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications that are within the spirit and scopeof the invention, as defined by the appended claims. Any combination ofthe above-described elements in all possible variations thereof isencompassed by the invention unless otherwise indicated herein orotherwise clearly contradicted by context.

It is claimed:
 1. A hydrogel formed by reaction of a hyaluronic acidhaving from 10% or less of its hydroxyl groups derivatized by reactionwith divinyl sulfone (“2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid”)with a thiol crosslinker having from two to eight thiol groups.
 2. Thehydrogel of claim 1, where the hyaluronic acid has a degree ofconversion of hydroxyl groups to 2-(vinylsulfonyl)ethoxy groups of about4-5% per disaccharide repeat unit.
 3. The hydrogel of claim 1, whereinat least one of: the hyaluronic acid has an average molecular weightranging from 700 to 3 million daltons, and the thiol-functionalizedpolyethylene glycol possesses a molecular weight ranging from about 250to about 20,000 daltons.
 4. The hydrogel of claim 1, where the thiolcrosslinker is a thiol-functionalized polyethylene glycol.
 5. Thehydrogel of claim 3, where the thiol-functionalized polyethylene glycolis polyethylene glycol dithiol (PEG dithiol).
 6. The hydrogel of claim4, where the thiol-functionalized polyethylene glycol possesses a polyolcore selected from glycerol, glycerol dimer (3,3′-oxydipropane-1,2-diol)trimethylolpropane, sorbitol, pentaerythritol, and hexaglycerol.
 7. Thehydrogel of claim 6, where the thiol-functionalized polyethylene glycolis four-armed and possesses a pentaerythritol core.
 8. The hydrogel ofclaim 1, comprising a percentage by weight (wt/wt) of polymer to waterranging from about 0.5 to 5.0 percent.
 9. The hydrogel of claim 1,comprising a bioactive agent.
 10. A composition comprising particles ofthe hydrogel of claim 1, in an aqueous solution of hyaluronic acid. 11.The composition of claim 10, where the hydrogel particles have sizesranging from about 0.10 to 3.0 millimeters.
 12. The composition of claim10, in the form of an aqueous slurry.
 13. The composition of claim 10,where the aqueous solution is saline.
 14. The composition of claim 10,further comprising a bioactive agent.
 15. The composition of claim 14,where the bioactive agent is a corticosteroid.
 16. The composition ofclaim 15, wherein the corticosteroid is triamcinolone acetonide.
 17. Thecomposition of claim 14, further comprising living cells.
 18. A methodfor treating acute or chronic inflammation by administering thecomposition of claim
 10. 19. The method of claim 18, where the acute orchronic inflammation is associated with rheumatoid arthritis, aninflammatory arthritis, and repetitive use.
 20. A method of preparing(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid, comprising (i)reacting hyaluronic acid with a molar excess of divinyl sulfone atambient temperature for a time period of under 3 minutes to therebyreact from 1% to 10% of hydroxyl groups on the hyaluronic aciddisaccharide repeat units with the divinyl sulfone.
 21. The method ofclaim 20, carried out in aqueous base.
 22. The method of claim 20, wherethe reacting step is carried out at a temperature from 20°-25° C. 23.The method of claim 20, wherein the reacting step is carried out for 10seconds to about 120 seconds.
 24. The method of claim 21, where theaqueous base is selected from aqueous sodium hydroxide and aqueouspotassium hydroxide.
 25. The method of claim 21, where the methodfurther comprises quenching the reaction by addition of acid.
 26. Amethod of preparing a lightly crosslinked hydrogel comprising reacting(2-(vinylsulfonyl)ethoxy)_(1-10%)hyaluronic acid with a thiolcrosslinker having from two to eight thiol groups in aqueous solution ata temperature ranging from 20° C. to 45° C.
 27. The method of claim 26,where the reacting is carried out at physiological pH.
 28. The method ofclaim 26, wherein the thiol crosslinker is sterilized prior to thereacting step.
 29. The method of claim 27, wherein following thereacting step, the resulting mixture is allowed to react for a period offrom 8 to 36 hours to thereby result in formation of a gel.
 30. Themethod of claim 26, carried out under sterile conditions.
 31. The methodof claim 26, further comprising adding an active agent to the aqueoussolution.
 32. The method of claim 31, wherein the active agent is acorticosteroid.
 33. The method of claim 32, wherein the corticosteroidis selected from triamcinolone acetonide, triamcinolone hexacetonide,triamcinolone benetonide, triamcinolone furetonide, and triamcinolonefuretonide.